Algae, Balance, Nutrients...
Contents:
- conceptual traps
by "Roger S. Miller" <rgrmill/rt66.com> (Tue, 28 Mar 2000)
- conceptual traps
by "Peter G. Aitken" <peter/pgacon.com> (Wed, 29 Mar 2000)
- Nutrients (aka, Roger & Me)
by "Dixon, Steven T. (BEn)" <stdixon/ben.bechtel.com> (Wed, 29 Mar 2000)
- Nutrients
by Roger Miller <rgrmill/rt66.com> (Wed, 29 Mar 2000)
- Musings
by Karen Randall <krandall/world.std.com> (Thu, 30 Mar 2000)
- re: Nutrients
by Roger Miller <rgrmill/rt66.com> (Thu, 30 Mar 2000)
- Musings
by "Roger S. Miller" <rgrmill/rt66.com> (Fri, 31 Mar 2000)
- an algae experiment
by "Roger S. Miller" <rgrmill/rt66.com> (Sun, 10 Jun 2001)
- an algae experiment
by "Roger S. Miller" <rgrmill/rt66.com> (Wed, 13 Jun 2001)
- Algae samples and overview
by Thomas Barr <tcbiii/earthlink.net> (Fri, 23 Feb 2001)
by "Roger S. Miller" <rgrmill/rt66.com>
Date: Tue, 28 Mar 2000
Folks,
This note isn't aimed at Michael -- he has just provided me with a soap
box to climb on. There have been any number of posts to which I could
write this same response.
On Tue, 28 Mar 2000, Michael Rubin wrote:
> I've got hair algae out the kazoo in my 50g and I was casting about
> looking for a magic bullit. There's really no such thing - magic
> bullits always come at a cost. I think the best idea for me is to
> hunker down and figure out what's missing in my nutrient balance.
CAUTION, strong opinions follow.
A lot of people on this group when faced with an algae problem (their own
or that of others who they are trying to help) have fallen into a similar
conceptual trap; they ask "what's missing?"
The answer to the question is patently obvious. THERE IS NOTHING MISSING.
If some essential component were missing then the algae wouldn't be
a problem.
No matter what you do with your tank there will always be something that
limits plant and/or algae growth. It may be light intensity, it could be
circulation, it could be any one of the essential elements.
Let's take an example that is limited by the availability of nitrogen.
The plants and algae grow at a rate that is determined by the rate that
plant-available nitrogen is added to the tank. All other essential
nutrients are (by definition) added at a higher rate relatve to the
demand and tend to accumulate in the tank. When you increase the
nitrogen supply you get more growth -- certainly more growth from the
algae and hopefully more growth from the plants. In fact you should get
a burst of growth that lasts until the excess accumulation of some other
essential element is depleted. In the meantime your tank may be a mess.
At some point the accumulated nutrients will be used up and the growth
rate will slow down. Whatever the growth rate settles down to will be a
*higher* rate than it was before you started adding extra nitrogen.
That's because all of the other potentially growth-controlling nutrients
are added at a higher rate than nitrogen was back when the nitrogen supply
was growth-controlling. This doesn't solve your problem.
As long as you're adding those nutrients to the water column you're
feeding both the plants and the algae and there's no reason to believe
that plants will be favored over algae. That initial burst of growth and
the subsequently higher growth rates may be seen in algae growth as easily
(or more easily) than in plant growth because the dissolved nutrients are
available to plants and to the algae.
There is another conceptual trap that victimizes people in this group, and
it seems to be closely related to the first problem. People try to manage
their tank with test kits. This approach seems to work for some but it's
a pretty long and winding route for others.
When you test nutrients in the water column you are -- under the best
scenario -- testing the nutrient supply that is available to algae and to
floating plants. The nutrient supply to rooted plants is something
different. The test kits don't necessarily work right and even the best
test kits may not give an accurate measure of nutrients that are available
to the algae and floating plants. The actual nutrient availability may be
higher (in the case of phosphorus) or lower (in the case of iron) then the
value indicated by a test kit. As a result, the common scenario probably
is substantially different from the best scenario.
The nutrient values you test in the water column certainly aren't the
nutrient levels available to rooted plants. Unless, or course, your
tank's substrate is inert and nutrient-free. Most aren't. Normally the
substrate can provide a substantial amount of the nutrient needs of
rooted plants. Iron and phosphorus tend to settle into the substrate.
Exchangeable nutrients like potassium, calcium and magnesium are
concentrated in the substrate by cation exchange.
You can only judge the nutrient supply to your plants by observing their
growth. If their growth is robust and healthy then their nutrient supply
is fine; it doesn't make any difference what the test kits say. If their
growth is weak and unhealthy then something - maybe a nutrient - is
missing and what your test kits tell you may or may not be useful.
What's more, some test kit results get passed around on this list with
little apparent thought to what they might mean. Dissolved iron
concentrations that are a substantial part of a ppm are probably more than
an order of magnitude above levels that are actually meaningful to your
plants. If you have those high levels and your plants are showing
symptoms similar to iron deficiency, what might that mean? I doubt
there's a plant on earth that evolved to required 20 or 30 mg/l of
potassium in the water it grows in. If your plants seem to need that
much, what might the problem be?
Roger Miller
P.S. Some possible answers to the iron question: 1) it's not iron
deficiency 2) the iron shown in the test isn't available to the plants 3)
the test result is bogus. A possible answer to the potassium question...
most natural surface water will contain only 2-3 ppm of potassium; higher
concentrations are provided in aquatic soils, and that's probably where
rooted plants satisfy most of their demand. You might be able to dose
your water up to a potassium concentration that would be normal in soil
pore water, but why would you?
by "Peter G. Aitken" <peter/pgacon.com>
Date: Wed, 29 Mar 2000
Roger's post makes some good points but it seems to ignore the apparently
well established fact that, in some tanks with algae problems, something
*IS* missing. Not "missing" as in totally absent, but as in not enough of.
I have seen lots of information to the effect that algae growth is
controlled in a tank where plant and algae growth are phosphate limited due
to the apparent superiority of plants over algae at extracting the
phosphate. If growth is not PO4 limited then it is limited by something
else, and adding that something else can be the one most important step in
algae control. In many cases, mine included, the missing substance was
nitrate. So, Roger is certanly right in that the solution to tank problems
is not always adding something, but sometimes it is.
Peter G. Aitken
by "Dixon, Steven T. (BEn)" <stdixon/ben.bechtel.com>
Date: Wed, 29 Mar 2000
Roger Miller's response to Michael Rubin's "what is missing" comment has
stirred me up quite a bit this morning. So I thought I would share some of
my thoughts. No personal attack on Roger is intended in any sense; in fact,
I'm delighted that Roger has "forced my hand" so-to-speak, and made me
rethink some of the rationales for my own views! :-) Roger's comments are
in quotes and my responses follow.
Roger:
"A lot of people on this group when faced with an algae problem (their own
or that of others who they are trying to help) have fallen into a similar
conceptual trap; they ask "what's missing?"
The answer to the question is patently obvious. THERE IS NOTHING MISSING.
If some essential component were missing then the algae wouldn't be a
problem."
Me:
I suspect that Roger may be right on this point about half the time. ;-)
Roger's note seems to be saying if you have an algae problem, ONE OR MORE
NUTRIENTS MUST BE IN EXCESS. (This statement is nothing more than a
necessary corollary of Roger's "nothing is missing" statement. Let's call
this Roger's Corollary! :-)) While I certainly think this is true in some
cases, it is by no means true in all cases, and certainly not patently
obvious in any but a very small percentage of cases. Let's start with an
example where Roger's Corollary IS TRUE. I can take a healthy, growing,
reasonably well-balanced, stable planted tank with minimal algae and wreak
havoc on that tank by adding large doses of excess iron to the water column.
Unfortunately, I have created this exact situation in my living room tank on
several occasions! ;-) The solution has been to reduce iron levels to lower
levels, say, under 0.05 ppm in the water column.
Now let's take a much more complicated situation where Roger's Corollary is
NOT TRUE. I have been quite surprised recently to learn that the presence
of significant levels phosphorus in the water column is not necessarily in
and of itself problematic. We now have numerous reports (including Karen
Randall's) which I have confirmed with my own anecdotal experiments that a
reasonably well-run planted aquarium can operate quite successfully with PO4
levels at least as high as 1 ppm (water column) SO LONG AS NITROGEN IS NOT
ALLOWED TO BECOME THE LIMITING NUTIENT. Let's suppose you have a chunk of
phosphorus in your tap water. Imagine trying eliminate that problem by
reducing phosphorus (as so many people try to do) while ignoring the hard
won knowledge (thank you Paul and Kevin) that one limits nitrogen in a
planted tank at one's own peril!
Back to Roger's original "nothing is missing" statement. What is Roger's
scientific justification for that statement? Answer: Leibniz Law, which
states that the limiting growth factor will limit plant growth. According
to Roger, nothing is missing because the algae is growing!!! If any
essential nutrients were missing, the algae wouldn't be growing, would it!
Say what? Nice hat trick Roger, but NO CIGAR! If growing buckets of algae
was our purpose I would say fine, let's declare victory and retire to the
nearest pub to lift a few. But we're trying to grow higher order plants,
more or less to the exclusion of most algae. Why aren't the higher order
plants growing? That should be the focus of our inquiry.
Roger:
"No matter what you do with your tank there will always be something that
limits plant and/or algae growth. It may be light intensity, it could be
circulation, it could be any one of the essential elements.
Let's take an example that is limited by the availability of nitrogen. The
plants and algae grow at a rate that is determined by the rate that
plant-available nitrogen is added to the tank. All other essential
nutrients are (by definition) added at a higher rate relative to the demand
and tend to accumulate in the tank. When you increase the nitrogen supply
you get more growth-certainly more growth from the algae and hopefully more
growth from the plants. In fact you should get a burst of growth that lasts
until the excess accumulation of some other essential element is depleted.
In the meantime your tank may be a mess."
Me:
This is where the rubber meets the road folks! Roger supposes a tank that
is nitrogen-limited, but has enough other nutrients. He says that nitrogen
limits both the growth of algae and higher order plants. He says that
increasing nitrogen will "certainly [result in] more growth from the algae."
WRONG! We have observed for years and years now that increasing nitrogen in
nitrogen limited situations will REDUCE ALGAE GROWTH, and increase higher
order plant growth. And those of us who have run amok playing around with
nitrogen also know that even monster amounts of nitrogen (say, 50 - 100 ppm
NO3) are not in and of themselves particularly problematic in an otherwise
well-run planted tank. (I have always assumed that this knowledge explained
why portions of Europe with very high nitrate levels in the tap water could
do so well with planted tanks. Recall that the large Dupla tank was
reported in "The Optimum Aquarium" to retain ~25 ppm NO3 with tap water
inputs of ~55 ppm, if memory serves.)
Before we leave this, what the hell happened to Leibniz Law in this example?
There wasn't much algae in the tank; we added some nitrogen; and we got even
less algae. Huh? While we didn't limit the other nutrients, could the
faster growing higher order plants have limited other nutrients? But if the
higher order plants result in some other nutrient(s) being limited, why are
they still growing? After all, as Roger (and Leibniz) says, if the
necessary nutrients were limited, the plants would not be growing, would
they? And if the higher order plants are growing, why aren't the algae
growing? Could the higher order plants be able to grab all of some
particular nutrient(s), store them in their tissue for later use, and as a
result starve out the algae? Could Leibniz Law be wrong? I DON'T KNOW the
answer to these questions, but I do think many of these observations have
been repeated for years by aquarists from around the world.
As an aside, when Claus Christensen was here on the West Coast, while he
paid homage to Leibniz, he went on to say that in practical terms Leibniz
law was somehow wrong. I have been trying for days now to recall and
analyze exactly what Claus said on this point, but can't get it clear in my
mind. If he made the same point in his East Coast speeches I would love to
hear your best understanding of the point Claus was making. While I can
dream up limiting factor theories that might explain why higher order plants
seem to be able to "outcompete" algae, in all honesty I'm completely baffled
by the notion.
Roger:
"At some point the accumulated nutrients will be used up and the growth rate
will slow down. Whatever the growth rate settles down to will be a *higher*
rate than it was before you started adding extra nitrogen. That's because
all of the other potentially growth-controlling nutrients are added at a
higher rate than nitrogen was back when the nitrogen supply was
growth-controlling. This doesn't solve your problem.
As long as you're adding those nutrients to the water column you're feeding
both the plants and the algae and there's no reason to believe that plants
will be favored over algae. That initial burst of growth and the
subsequently higher growth rates may be seen in algae growth as easily (or
more easily) than in plant growth because the dissolved nutrients are
available to plants and to the algae."
Me:
In point of fact, we observe the exact opposite in case after case after
case. The higher order plants do grow better than algae as we ease the
nitrogen limited situation.
Roger:
"There is another conceptual trap that victimizes people in this group, and
it seems to be closely related to the first problem. People try to manage
their tank with test kits. This approach seems to work for some but it's a
pretty long and winding route for others."
Me:
Test kits can be an invaluable aid to tank observation. The most recent
example for me concerns phosphorus. Had I not taken my Hach PO4 test kit to
Marin County to measure Tom Barr's tap water in connection with the feature
article on Tom for the first issue of Planted Aquaria Magazine (see, I got
it in Dave! :-)) I'm not sure it would have dawned on me what a valuable
contribution a little bit of PO4 in the water column can be for a variety of
plants. This, I believe, turns out to be the secret to what those of us in
Northern California have always referred to as "Marin's magic water"! That
is to say, in an otherwise well-run high-growth planted aquarium, one can be
phosphorus-limited to the detriment of the plants.
And while there are half a dozen important "rules of thumb" for the proper
use and analysis of test kits and their results, like everything else in
life, after you figure it out, it's pretty easy. There is no truth
whatsoever to the MAD-SCIENTIST-RUN-AMOK image that has been applied to the
intelligent use of test kits.
Roger:
"When you test nutrients in the water column you are-under the best
scenario-testing the nutrient supply that is available to algae and to
floating plants. The nutrient supply to rooted plants is something
different. The test kits don't necessarily work right and even the best
test kits may not give an accurate measure of nutrients that are available
to the algae and floating plants. The actual nutrient availability may be
higher (in the case of phosphorus) or lower (in the case of iron) then the
value indicated by a test kit. As a result, the common scenario probably is
substantially different from the best scenario.
The nutrient values you test in the water column certainly aren't the
nutrient levels available to rooted plants. Unless, or course, your tank's
substrate is inert and nutrient-free. Most aren't. Normally the substrate
can provide a substantial amount of the nutrient needs of rooted plants.
Iron and phosphorus tend to settle into the substrate. Exchangeable
nutrients like potassium, calcium and magnesium are concentrated in the
substrate by cation exchange."
Me:
YEP, you can't tell much about substrate nutrients by testing the water
column! Except Leibniz' point, if they're growing, they must have what they
need.
Roger:
"You can only judge the nutrient supply to your plants by observing their
growth. If their growth is robust and healthy then their nutrient supply is
fine; it doesn't make any difference what the test kits say. If their
growth is weak and unhealthy then something - maybe a nutrient - is missing
and what your test kits tell you may or may not be useful."
Me:
Uh-oh, can't be anything missing if the algae is growing though, right
Roger? :-) My apologies, couldn't restrain myself on that one! While it is
true enough that if the growth is robust and healthy the nutrient supply is
fine, how do we know by visual observation alone what the problem is if the
tank is a wreck? You suppose, wrongly in my view, that some or other
nutrient is always in excess (if the algae is growing). But which nutrient
is it and how do you tell the difference between one excess nutrient and
another. Or heaven forbid, combinations and permutations of multiple excess
nutrients? The mind reels. I wish I could do that but I can't, and some
times my test kits help me eliminate certain issues and improve the
likelihood that a particular course of action will help the aquarist with a
problem.
Roger:
"What's more, some test kit results get passed around on this list with
little apparent thought to what they might mean. Dissolved iron
concentrations that are a substantial part of a ppm are probably more than
an order of magnitude above levels that are actually meaningful to your
plants. If you have those high levels and your plants are showing symptoms
similar to iron deficiency, what might that mean? I doubt there's a plant
on earth that evolved to required 20 or 30 mg/l of potassium in the water it
grows in. If your plants seem to need that much, what might the problem
be?"
Me:
Not so fast. Claus Christensen and I talked non-stop for 10 hours last
Thursday as we drove to and from and toured the Monterey Bay Aquarium. We
talked about potassium at some length and I was surprised to hear Claus say
that many if not most of our aquatic plants do well with 10 - 15 ppm
potassium, but that several species do much better with 25 - 35 ppm
potassium in the water column. So to answer your specific question: They
just might like the extra potassium :-) which is not to say it might be just
as well to add some potassium in the substrate.
While I hate to be the bearer of bad news, I can report more or less for
sure, that 20 - 30 ppm of potassium in the water column is not necessarily
EXCESS and in an otherwise well-run aquarium, presents no algae issues that
I'm aware of.
It occurs to me that perhaps Roger has his own version of "magic Marin
water" and so he naturally thinks about excess nutrients, while those of
working with very soft pure waters constantly think about what nutrients to
add!
Time for some lunch. It's been a fun morning, and I needed the break from
way too much work. Thanks Roger.
Regards, Steve Dixon in San Francisco where the sun is shining brightly
by Roger Miller <rgrmill/rt66.com>
Date: Wed, 29 Mar 2000
Well, I snipped about as much as I could and this still got really, really
long. I hope it's worth it :).
On Wed, 29 Mar 2000, Steve Dixon wrote:
> Roger Miller's response to Michael Rubin's "what is missing" comment
> has stirred me up quite a bit this morning. So I thought I would
> share some of
> my thoughts. No personal attack on Roger is intended in any sense; in fact,
> I'm delighted that Roger has "forced my hand" so-to-speak, and made me
> rethink some of the rationales for my own views! :-) Roger's comments are
> in quotes and my responses follow.
Gee, always glad to be of service :)
> Roger:
> "A lot of people on this group when faced with an algae problem (their own
> or that of others who they are trying to help) have fallen into a similar
> conceptual trap; they ask "what's missing?"
> The answer to the question is patently obvious. THERE IS NOTHING MISSING.
> If some essential component were missing then the algae wouldn't be a
> problem."
> Me:
> I suspect that Roger may be right on this point about half the time. ;-)
> Roger's note seems to be saying if you have an algae problem, ONE OR MORE
> NUTRIENTS MUST BE IN EXCESS. (This statement is nothing more than a
> necessary corollary of Roger's "nothing is missing" statement. Let's call
> this Roger's Corollary! :-))
Hmm. I hope that name doesn't get propogated, because I don't think I
agree with it. For one thing, nutrient concentrations may not be the
cause of the algae problem at all. For another, if we're going to take
Leibnitz' rule to it's extreme, when one nutrient is growth-controlling
then ALL other nutrients are present in excess. That fact is of rather
trivial value because excess nutrients aren't usually a problem.
[snip]
> Back to Roger's original "nothing is missing" statement. What is Roger's
> scientific justification for that statement? Answer: Leibniz Law, which
> states that the limiting growth factor will limit plant growth. According
> to Roger, nothing is missing because the algae is growing!!!
Actually, the statement doesn't depend on Leibnitz at all. It's based on
the composition of the algae. Certain elements are essential for the
existence and growth of algae (and plants for that matter). The algae
have to contain all of them, or the algae isn't there. My statement is
based on the simple fact that if the algae is there then all of the
nutrients that are essential to its existence are also there. This says
nothing at all about growth rates. And yes, it is tautological that for
the algae to grow, all of its essential nutrients must be present and
available to the algae. That is the definition of "essential nutrient".
The same thing applies to plants.
[snip]
> Why aren't the higher order plants growing? That should be the focus
> of our inquiry.
Did someone say that the higher order plants weren't growing? Plants can
grow quite well in the presence of algae. If they aren't, then there
might be quite a few reasons why not.
[more snips]
> Roger supposes a tank that
> is nitrogen-limited, but has enough other nutrients. He says that nitrogen
> limits both the growth of algae and higher order plants. He says that
> increasing nitrogen will "certainly [result in] more growth from the algae."
> WRONG!
Actually, if it doesn't, then nitrogen wasn't growth limiting to start
with. The functional definition of the growth limiting nutrient is "the
nutrient that when added produces the largest change in the rate of
growth". This definition doesn't depend on Leibnitz. I think the
definition can be attributed to Gaudy and Gaudy (Environmental
Engineering, McGraw Hill, etc. etc).
I'm not sure I want to keep dragging Karen into this, after all she's
perfectly capable of speaking for herself. Just the same, I recall a
thread a couple years ago where she agreed that some people who undertake
additions of potentially growth limiting nutrients *do* see initial
explosive growth of algae. In those cases where they don't, either they
added the wrong nutrient or the tank passed through the "explosive growth"
phase and back into nutrient limited growth quickly enough that it wasn't
a problem. I think this latter conclusion may have been my conclusion
rather than hers, but I can't recall for sure.
> We have observed for years and years now that increasing nitrogen in
> nitrogen limited situations will REDUCE ALGAE GROWTH, and increase higher
> order plant growth.
Some people have reported success with this method, and other people have
not. Where it does work the reduction in algae growth is thought to be a
secondary effect of causing some other nutrient to become limiting, plus
the tertiary effect of competition. It isn't a direct effect of adding
nitrate. As in most cases where the solution is indirect, results can be
inconsistent. A more direct approach would be to reduce the concentration
of some other dissolved nutrient (phosphorus, for instance) to the point
where it becomes growth limiting. Since this is a direct approach the
results should be more consistent and predictable.
[snip]
> As an aside, when Claus Christensen was here on the West Coast, while he
> paid homage to Leibniz, he went on to say that in practical terms Leibniz
> law was somehow wrong.
I think there are quite a few possible problems with Leibnitz, especially
when applied to individual plants or to short periods of time. It is of
course completely wrong if you apply it to a case where nutrient
concentrations aren't growth limiting. Right or wrong this lists has a
fairly long history of depending on it as a fairly simple model that
explains some of the conditions we see.
> While I can dream up limiting factor theories that might explain why
> higher order plants seem to be able to "outcompete" algae, in all
> honesty I'm completely baffled by the notion.
If you go back to the Davis and Brinson article, there's an article that
shows (again, for natural conditions) that under oligotrophic and
mesotrophic conditions - low to moderate production rates, generally with
low dissolved nutrient concentrations - that plants compete very well with
algae. Algae do better under eutrophic and hypereutrophic conditions
where total production rates are higher and dissolved nutrients are
generally higher. I can think of several specific mechanisms for that and
some might actually be relevant to aquariums.
[snip]
> Test kits can be an invaluable aid to tank observation.
I've got some successful, well-planted tanks that I've never used a test
kit on. I've got another that I haven't tested for anything in 5 years or
so. This is a hobby and I encourage you to spend your time in it in any
way that gives you the greatest enjoyment. You may find them invaluable;
I find them mostly dispensible. And yes, I do have test kits and I do
occasionally use them.
[did I snip something here?]
> While it is true enough that if the growth is robust and healthy the
> nutrient supply is fine, how do we know by visual observation alone
> what the problem is if the tank is a wreck? You suppose, wrongly in my
> view, that some or other nutrient is always in excess (if the algae is
> growing). But which nutrient is it and how do you tell the difference
> between one excess nutrient and another.
Um, if the plants aren't growing well then probably nutrient excess isn't
the problem. Unless of course it has reached toxic levels or caused such
imbalance that usual nutrient uptake is disturbed. In that case there
should be symptoms.
> Or heaven forbid, combinations and permutations of multiple excess
> nutrients? The mind reels. I wish I could do that but I can't, and some
> times my test kits help me eliminate certain issues and improve the
> likelihood that a particular course of action will help the aquarist with a
> problem.
I'll give you this. Test kits can be useful for trouble shooting. So can
careful observation of the plants, and a review of changes and maintenance
practices in the tank. My preference is to get as much as possible from
direct observation, and to test only occasionally. This is certainly a
different case from using test kits in the regular micro-management of a
tank.
> Claus Christensen and I talked non-stop for 10 hours last
> Thursday as we drove to and from and toured the Monterey Bay Aquarium.
I'm envious.
> We talked about potassium at some length and I was surprised to hear
> Claus say that many if not most of our aquatic plants do well with 10
> - 15 ppm potassium, but that several species do much better with 25 -
> 35 ppm potassium in the water column. So to answer your specific
> question: They just might like the extra potassium :-) which is not
> to say it might be just as well to add some potassium in the
> substrate.
As I recall, Tropica's plants are grown hydroponically. It makes sense
that the hydroponic solution would be similar in composition to soil pore
water. I'm not sure my fish want to live in a hydroponic solution so I
try to restrict high nutrient levels to the substrate.
> While I hate to be the bearer of bad news, I can report more or less for
> sure, that 20 - 30 ppm of potassium in the water column is not necessarily
> EXCESS and in an otherwise well-run aquarium, presents no algae issues that
> I'm aware of.
None that I'm aware of either. Excess nutrients aren't a problem unless
they reach toxic levels. *With* the simplifications of Leibnitz' rule and
*if* nutrients are growth-limiting, and *if* the growth rate of algae is
high enough to become a nuisance then it's because the *limiting* nutrient
- -- not any excess nutrient -- is too readily available.
> It occurs to me that perhaps Roger has his own version of "magic Marin
> water" and so he naturally thinks about excess nutrients, while those of
> working with very soft pure waters constantly think about what nutrients to
> add!
Certainly there are different approaches required for hard water and for
soft water. Unfortunately my water is soft, but far, far from pure.
Thanks, Steve for the exchange. It's been a delight.
Roger Miller
by Karen Randall <krandall/world.std.com>
Date: Thu, 30 Mar 2000
Roger wrote:
>I'm not sure I want to keep dragging Karen into this, after all she's
>perfectly capable of speaking for herself.
Ahhh, but you guys have been doing so well on your own. For heavens sakes,
you're not even fighting with each other! ;-) I haven't seen much to
strongly disagree with, and besides I've got a migraine. I'm only reading
this because I've given up on sleeping. (for the moment)
>Just the same, I recall a
>thread a couple years ago where she agreed that some people who undertake
>additions of potentially growth limiting nutrients *do* see initial
>explosive growth of algae
_Sometimes_ I think it depends on the type of algae you are trying to deal
with. I don't think you'll see a marked increase in cyanobacteria, for
instance, when correcting a nitrogen deficiency.
>Algae do better under eutrophic and hypereutrophic conditions
>where total production rates are higher and dissolved nutrients are
>generally higher. I can think of several specific mechanisms for that and
>some might actually be relevant to aquariums.
My problem, and the reason I've chosen until now to sit back and just see
what you guys had to say is that from what I can see, basically _all_ our
aquariums would qualify as eutrophic. But UNLESS we keep nutrient levels
up there, our plants done' grow particularly well. I don't know why this
is, and I don't know why we are able to maintain tanks in this condition
without excessive algae problems, but I'm sure it is so.
I think that Steve P. hit on at least part of the answer, and that is that
we also tend to keep algae grazers in the tank. But that's not the whole
answer either. One of our tanks is a 10 gallon tank housing a large
axolotl. The tank has a large but slow growing clump of Java Fern on one
end, and smaller slow growing clump of Bolbitis on the other end, and
Salvinia floating on the surface. No CO2, small internal power filter that
gets changed when I feel guilty enough, (which is also when I do a water
change) Thin layer of pea-sized river gravel, no fertilizers of any sort.
Heck, there's not even a heater in the tank. The axolotl eats about six
night crawlers and sometimes a feeder goldfish or two each week. There is
some nutrient export in that every couple of weeks I do remove a few
handfuls of Salvinia. I don't know what the nutrient levels are in the
tank, but I'd be willing to bet that my test kits don't go that high. When
I remove the Salvinia, I usually also wipe a small amount of diatoms off
the glass. There is NO other algae in the tank. Why? If you told me you
were going to set up a tank of this size, with an animal that large, I
would have said that if you wanted plants and not an algae farm you'd
better be prepared to do MAJOR water changes.
Steve D wrote:
>> Test kits can be an invaluable aid to tank observation.
Roger wrote:
>I've got some successful, well-planted tanks that I've never used a test
>kit on. I've got another that I haven't tested for anything in 5 years or
>so. This is a hobby and I encourage you to spend your time in it in any
>way that gives you the greatest enjoyment. You may find them invaluable;
>I find them mostly dispensible. And yes, I do have test kits and I do
>occasionally use them.
I agree with both of you, and lean more heavily in Rogers direction. I
have test kits, but use them for the most part diagnostically. I don't go
to the Dr. for blood tests to tell me if I'm eating right. I go for tests
only if I already think there's something wrong with me. That's how I feel
about test kits. Yes, Steve, I agree that if I walk in cold to diagnose a
problem in someone else's tank, test kits can give you a lot of useful
troubleshooting information very quickly. But I also agree with Roger,
that in my own tanks, I use them very, very rarely. In fact, most of the
times that I _have_ used them in the past few years is to confirm what my
eyes are already have been telling me, because I feel guilty if I can't
assign numbers to these things when reading or talking to someone on the APD.
(I still have a big problem with the discrepancies I find between the need
for iron in my tanks vs. the very low test levels maintained by many people
on the list)
Steve wrote:
>> While it is true enough that if the growth is robust and healthy the
>> nutrient supply is fine, how do we know by visual observation alone
>> what the problem is if the tank is a wreck?
Actually, I find I'm pretty good at that too. I can usually make a pretty
good guess at what's going on between a visual inspection and questioning
the owner about maintenance practices. But I do like the back-up of a few
test kits. Particularly pH, KH, phosphate and nitrate.
Roger wrote:
>My preference is to get as much as possible from
>direct observation, and to test only occasionally. This is certainly a
>different case from using test kits in the regular micro-management of a
>tank.
I agree completely. That said, I _don't_ think that Steve is one of those
who tries to micromanage with test kits. I think he's just curious about
what's going on. I _do_ think there are people on the list who take
testing too far. But there are also people who jump on every single
bandwagon that comes along here.<g>
Roger wrote:
>As I recall, Tropica's plants are grown hydroponically. It makes sense
>that the hydroponic solution would be similar in composition to soil pore
>water. I'm not sure my fish want to live in a hydroponic solution so I
>try to restrict high nutrient levels to the substrate.
Tropica's SALES plants are grown hydroponically. Believe me, Claus has
extensive experience with aquatic plants grown under "normal" aquarium
conditions, both in test tanks and as someone who has been an aquarist with
_planted_ tanks since he was 7 years old. That's what makes Claus such a
wealth of information. (besides the fact that he's just a really nice guy)
He's knows aquatic plants and their culture from all perspectives.
There. See, I added my $.02, and it didn't make a bit of difference. I
don't know the answers any more than you guys do ;-)
Karen
by Roger Miller <rgrmill/rt66.com>
Date: Thu, 30 Mar 2000
On Thu, 30 Mar 2000, Steve Dixon wrote:
> Fortunately, I think Roger Miller and I have just about exhausted our
> knowledge of the topic we have been discussing. Just a couple of additional
> points and my head will be empty for sure! :-)
The installments are getting shorter. I imagine the list can only be
grateful :).
> Roger: "That fact [of Leibniz Law] is of rather trivial value because
> excess nutrients aren't usually a problem." And also, "Um, if the plants
> aren't growing well then probably nutrient excess isn't the problem." So if
> it is patently obvious that NOTHING IS MISSING (yesterday's note) and excess
> nutrients are usually not a problem, what on earth are we talking about? Are
> the conditions always "optimum" (uh-oh) and we either have algae or we
> don't! You're leading me by the nose in tautological circles. And it must
> be Groundhog's Day! :-)
Well, what I was talking about was that rapid algae growth means that all
of the nutrients necessary for algae growth (likewise, for plant growth)
are present in the water. Nothing is missing.
> Roger: "Some people have reported success with [limiting nutrients other
> than nitrogen], and other people have not. Where it does work the reduction
> in algae growth is thought to be a secondary effect of causing some other
> nutrient to become limiting, plus the tertiary effect of competition. It
> isn't a direct effect of adding nitrate." Of course it's the direct affect
> of adding nitrate. No other variables are changed. Nitrate is added and
> the algae declines.
The only mechanism I can think of that would account for this directly
would be toxicity. I don't think that nitrate is particularly toxic to
algae, so it leaves me looking for indirect mechanisms. The mechanism
that Paul and Kevin proposed for the PMDD regime was an indirect one: 1)
dosing with everything but phosphorus made phosphorus the limiting
nutrient (assuming adequate light, CO2, water movement and so on); 2)
competition for phosphorus forced its concentration to low values; 3)
plants were better than algae at competing for low phosphorus levels, so
the plants out-compete the algae. Cool. When it works.
> Roger: "With* the simplifications of Leibnitz' rule and *if* nutrients are
> growth-limiting, and *if* the growth rate of algae is high enough to become
> a nuisance then it's because the *limiting* nutrient -- not any excess
> nutrient-is too readily available." Sorry to be dense, but say what! The
> limiting nutrient is too readily available, but no nutrient is in excess!!!
> I don't have a clue what you're trying to say here.
The fact that some nutrient is growth-limiting doesn't mean the nutrient
is absent. The higher the concentration of the growth-limiting nutrient
(or the greater its availability) the faster the algae and plants will
grow. In this simplest assessment it's only the limiting nutrient that
matters. All other nutrients are available in sufficient supply so that
they don't limit growth.
Roger Miller
by "Roger S. Miller" <rgrmill/rt66.com>
Date: Fri, 31 Mar 2000
On Fri, 31 Mar 2000, Karen Randall wrote:
> My problem, and the reason I've chosen until now to sit back and just see
> what you guys had to say is that from what I can see, basically _all_ our
> aquariums would qualify as eutrophic. But UNLESS we keep nutrient levels
> up there, our plants done' grow particularly well. I don't know why this
> is, and I don't know why we are able to maintain tanks in this condition
> without excessive algae problems, but I'm sure it is so.
I've mused about this myself quite a bit and I conjecture that the reasons
are mostly ecological. In nature aquatic plants grow in settings as
different as murky slime-bottomed estuaries and fresh mountain spring
floored with fractured bedrock. But the best growth seems to be in fairly
clean water over silty organic sediments. The clean water allows for
bright light penetrating into deep water and the silty sediments provide a
great nutrient-holding capacity and an enormous level of biological
activity (worms, chironomids, molluscs etc. and their whole supporting
casts of creepy-crawlies) that constantly cycle nutrients through reactive
and readily plant-available forms.
The plants growing naturally thus have a constant and easily available
supply of nutrients from the substrate and enough energy (from the
sunlight) that they can easily apply that energy to actively import
nutrients that impedes their growth.
In contrast, our substrates are typically coarse-grained with little
nutrient-holding capacity and we either fail to introduce or actively
discourage all but a very few of the critters that might otherwise live
there. We provide out tanks with the minimum amount of light necessary to
grow a variety of plants, so many of them are left with little capacity to
actively import nutrients that are in short supply. We offset those
limits by giving our plants high concentrations of nutrients and since
most of us are also maintaining fish in our tanks we use nutrients that
are in chemically stable, less readily-available forms.
So our tanks typically have dissolved nutrient concentrations that are sky
high compared to natural waters; eutrophic would be an understatement.
Some of us have ways to keep algae from taking over in their tanks
like it would in nature and many of us read this list to find out how they
do it.
I can think of several factors that in contrast to natural conditions may
discourage algae growth in our tanks. Generally these are:
1) limited light -- this prevents any algae species that requires periods
of intense light from growing in our tanks and limits the amount of energy
the algae can apply to its needs.
2) grazing -- all natural systems support grazing but in our tanks we can
select for specific grazers (including microscopic grazers) and we can
eliminate predatory controls on their population.
3) disease -- there are bacterial and (as someone else pointed out
recently) also viral controls on algae; perhaps in the closed confines of
our tanks these controls are very important.
4) unreactive nutrients -- while our nutrient levels are very high, we
tend to use nutrients in forms (like nitrate, and chelated metals) that
aren't readily available. This is compounded by fairly low light.
5) unbalanced nutrients -- our tanks may contain very high levels of most
nutrients but low levels of one or two specific nutrients (e.g. phosphorus
and/or iron). Alternatively, those nutrients migh be restricted to the
substrate where the algae can't get it them. I think this is a distinctly
unnatural conditions and one that has to be actively maintained in our
tanks; it isn't likely to happen by itself.
I'm sure there's other reasons, but those are the ones that come to mind
right now.
Roger Miller
by "Roger S. Miller" <rgrmill/rt66.com>
Date: Sun, 10 Jun 2001
Folks,
For a while now I've been chasing the idea that at least some algae
problems can be related to organic compounds in the water. The general
thinking goes like this:
1) Some (but not necessarily all) algae can live in the dark by using
glucose and other soluble organics in the water.
2) Aquatic plants "leak" soluble organic material into the water.
There's even some published speculation that this behavior evolved to
encourage attached algae communities (herbivores would then eat the
attached algae, and leave the plant alone).
3) Terrestrial plants, when deficient in nitrogen, phosphorus or sulfur
can photosynthesize, but fail to use the simple sugars produces by
photosynthesis; instead, the sugars accumulate in the plant and lead to
anthocyanin (reddish-purple pigment) in the leaves and stems.
4) Aquatic plants should behave under nutrient stress like terrestrial
plants, but I reason that rather than accumulating the sugars, they will
probably leak the sugars back into the water. This leaking may help
explain why I don't usually see anthocyanin buildup in aquatic plants
that otherwise seem to be deficient in nitrogen or phosphorus. It's
perhaps interesting but irrelevant that stressed algae leak large
amounts of soluble organics.
5) Algae are more efficient than plants at concentrating dissolved
nutrients, so in the case where both plants and algae depend on the same
nutrient supply, nutrient stress and loss of organics should effect
plants before it effects algae.
6) The sugars lost by a nutrient-stressed plant can be used by algae; it
will act as a suppliment for the algae and allow them to grow at rates
and under conditions (low light, in particular) where they wouldn't
normally thrive.
If the last item could be proven true, then we might be able explain
some of our toughest algae problems, and in particular might explain how
it is that we can make algae disappear by fertilizing an aquarium.
Well-nourished plants stop losing sugars and without the extra subsidy
from the plants the algae no longer thrives and start to disappear.
So that's the theory. Of the items above, 1-3 are supported in the
scientific literature. There's a problem with applying item 1 (see
below), but otherwise I'll just regard 1-3 as facts.
Item 5 is also supported in the literature, but the case where both
plants and algae are dependent on the same nutrient supply is fairly
hypothetical. It generally doesn't occur in nature where plants use a
supply of nutrients in the soils that isn't available to algae. It
comes close to being true in aquariums where the principle nutrient
supply is added to the water column.
Item 4 is supported qualitatively by my own observations. It could be
supported more quantitatively by monitoring DOC (Dissolved Organic
Carbon, or just adsorbance at 254 nm in a spectrophotometer) in a
planted aquarium. If correct, then DOC in an aquarium should be low
when the plants are completely nourished and should be higher when the
plants are deficient in nitrogen or phosphorus. A more rigorous support
would be possible by determining the actual sugars in solution, but that
would be more difficult.
Item 6 is the conclusion. It could be supported by proving item 4 and
showing that algae growth rates and occurance correlate statistically
with the changes in DOC in an aquarium.
One of the weaknesses of all this reasoning is that we don't know if our
common nuisance algae actually can use simple sugars; that's the problem
with appying item 1. So last week I set out to see if some of our
common nuisance algaes can use dissolved sugars. I only have a few in
my tanks, so that's what I used.
I set up two 1-quart bottles in a simple controlled experiment. Each
bottle was covered in duct tape to exclude light. One was filled with
dechlorinated tap water and the other was filled with dechorinated tap
water plus 1/24th of a 5 gram glucose tablet -- about 200 mg of
glucose. The water in both containers was changed every two days.
I took three algae samples from my tanks and split them more-or-less
equally between the containers. One algae sample was a green,
long-stranded hair algae that grows unattached in a sunlit bowl with my
emersed sword plant. One algae sample was a short-stranded green hair
algae that grows in bright artificial light or dim light and forms
loosely attached, dense mats on the substrate and tufts in protected
areas on leaves and aquarium equipment. The last sample was black brush
algae. This is a red algae that grows under bright or dim light (but is
more characteristic of dim light) and is firmly attached.
I placed the bottles in a cabinet, put an air stone in each container
and bubbled air through them for a week. I observed the contents of
each bottle every day. Today (a week after starting the test) I dumped
the bottles to see what I had left.
There were several problems with the experiment. Mostly, the agitation
caused by aeration made the hair algaes get matted and entangled.
Future attempts need to use less agitation and keep the samples
separated. Second, I didn't have any way to measure or weigh the
samples and hoped for clear-cut results such as the complete
disappearance of the failed samples. That didn't happen, so any
conclusion depends on my recollection of the sample size and a
comparison of the samples. Finally, the glucose concentration probably
needs to be smaller to more nearly represent conditions in an aquarium.
So, after it was all done, here's what I noticed and what it might mean.
I half-expected that one or both bottles would be taken over by blue
green algae. That didn't happen, and I'm not sure why. That may
indicate that whatever BGA accompanied my samples didn't use glucose. I
find that a little surprising.
The long-stranded hair algae in both bottles was smaller than it started
out to be. That could be just because it was matted and twisted by the
aeration, but my sense is that there was about a 50% loss of mass in
both bottles. This would indicate no response to glucose. This doesn't
surprise me much, as in my tanks the algae occurs only in bright light.
The short-stranded hair algae disappeared completely from the bottle
without glucose. Most of the sample appeared to break up into loose
fibers after the first 24 hours of the test. Some of the short-stranded
algae may still have been present but unobserved at the end of the
test. If it was present then it was tangled with the long-stranded
algae. The short-stranded hair algae was still present in the bottle
with glucose. It was loosely attached to the bottom of the bottle and
appeared to have at least as much mass as it started with. This
suggests that the short-stranded hair algae did use the glucose.
The black brush algae was still clearly identifiable in both bottles,
but in the bottle without glucose it appeared to lose about half of its
mass. Some of that BBA sample could have become entangled with the long
hair algae. The original mass appeared to be entirely intact in the
bottle with glucose, but it didn't appear to grow. So BBA appeared to
use the glucose.
There are enough problems here that I can't draw any real conclusions.
Ideally, if better experiments in the future prove out the results of
this test then we will have not just an explanation for some of out
sticky algae problems, but a new approach (organics control) for
cleaning up and controlling nuisance algae.
Roger Miller
by "Roger S. Miller" <rgrmill/rt66.com>
Date: Wed, 13 Jun 2001
On Wed, 13 Jun 2001, Christopher Newell wrote:
> That was an interesting post a couple of days back.
> I've been trying to digest it. I'm out of my element
> with most of this discussion, but wanted to comment.
Thanks for taking the time. I hoped to get enough feedback to see if I
needed to change my thinking.
> In a discussion with friends, it was pointed out to me
> that plants (which includes algae) can make use of
> sugars, amino acids, etc. - it is the basis of tissue
> culture.
The ability of plants (and algae) to take simple carbohydrates out of
solution is also the basis for Seachem's Excel product. While I have
found plenty of references that indicate *some* algae will use sugars that
they get out of the water I haven't found any author willing to say that
they *all* will. I expect conciderable variability.
As a note, I'm using the term "sugar" to refer to most simple
carboyhydrates.
> You are referring to a nutrient stressed situation.
> Im assuming that you are referring to high light tank
> with co2 supplementation and without adequate nutrient
> supplementation, because most planted fish tanks
> have an abundance of nutrients. The low tech planted
> fish tank is where most folks experience algae
> problems. But again, you are talking about a
> nutrient stressed situation.
Specifically I'm referring to planted tanks low in nitrogen and/or
phosphorus. This could be high or low in other factors, though the
problem is likely to be more evident in tanks where there is a high rate
of photosynthesis.
> You mention that the plants might be leaking sugars
> into the water, which makes this sugar food source
> available for algae to use. This is difficult for me
> to follow, but certainly, Im not saying that you are
> wrong.
As near as I can tell from the literature it is well-known that aquatic
plants do leak organics into the water. There may be an evolutionary
advantage to that behavior.
> During lean times when plants are nutrient
> stressed you conjecture that our plants begin to make
> sugars as terrestrial plants do. I would think that
> the plant is making sugar for its own use. The plant
> controls the water flow into and out of the tissue.
> If the sugars leak then wouldnt it be in miniscule
> quantities?
All plants (aquatic or terrestrial) and algae make sugars any time the
light is bright enough. Simple carbohydrates are the initial product of
photosynthesis. The plant normally builds all of its components out of
those simple sugars. Phosphorus is necessary in the intermediate steps of
carbohydrate synthesis and for the plants to make proteins and other
biochemicals they need other nutrients as well. That's were nitrogen,
more phosphorus and most of those other essential elements fall in.
If nitrogen or phosphorus is deficient then the plant can't make proteins
and other classes of biochemicals and the excess simple sugars build up.
Some of the sugars can be converted to woody material and some can be
stored, but not all of it. In terrestrial plants the excess sugars build
up; I think that after some point aquatic plants tend to lose the sugars
rather than retain them. Terrestrial plants might leak them too if they
could, but they since they aren't emersed in water it isn't so easy for
them to lose the sugar.
I have never read of a mechanism by which a plant could effectively slow
down the rate of photosynthesis, so the simple sugars are produced
regardless of whether the plant needs them, can use them, or has any way
to store them. Even detached leaves will continue to photosynthesize. At
some point the plant must start leaking those sugars back into the water.
The leakage rate would not be miniscule; the plant could potentially leak
all of the sugars that it synthesizes.
I think I've seen that happen in phosphate-deficient vals. Given CO2 and
light they bubbled and bubbled, which is direct evidence for
photosynthesis, but despite the evident photosynthesis there was no
evident growth for weeks. Where did they put the products of their
photosynthesis? Vals don't have noticable storage organs and there was no
anthocyanin evident in the leaves to indicate sugar buildup in the leaves.
I concluded that the plants leaked almost everything they
photosynthesized. There were concurrent algae problems.
> The sugars need to be leaked by the
> plant and absorbed by opportunistic algae. This is a
> byproduct of a byproduct, as it were. Would this
> effect be measurable in an aquarium? I would think
> that the bacteria bed would make use of the sugar
> before the algae would.
The "leaked" sugars could represent a big part -- even all -- of the
plants primary production, so this is a potentially major process, not
simply a byproduct of a byproduct.
The opportunistic algae are another matter entirely. Algae are highly
evolved specialists. The algae that live in our tanks probably have some
specific adaptation that allows them to thrive under aquarium conditions.
Out of all the thousands of algae species out there, there are only a few
that thrive to nuisance levels in our tanks. I suspect that the ability
to use dissolved sugars is one of the factors that determines which algae
species thrive in our tanks. So the algae aren't merely opportunists,
they are specialists at exploiting the conditions we provide them.
You are right that bacteria should be able to out compete algae for the
dissolved sugars, and in a natural environment that is probably what
happens. At least that is what I was told by a biology professor at the
local University who has a special interest in organic compounds in
natural systems.
We aren't dealing with natural conditions. Instead I'm talkin about
pathologic conditions brought on by nutrient stress in a mostly closed
environment. I think the availability of those sugars would be so high
that competition would be irrelevant. The sugar would be available to
both algae and bacteria.
This theory isn't really a "revolution" in thinking. Instead it's just a
different way of explaining a number of observations that are otherwise
difficult to understand; like how it is you can add nutrients and
discourage algae, which lots of us have found to work.
Roger Miller
by Thomas Barr <tcbiii/earthlink.net>
Date: Fri, 23 Feb 2001
I just did a quick overview of several algae samples given to me by some
folks.
The BGA that folks, myself included, have postulated thrive in an N limited
environment are not the kind of cyano's that can use atmospheric N2 by
breaking the N2 dimer using nitroansae enzyme. A heterocyst is required for
N2 bond breaking. I looked at about 10 different samples from a variety of
different tanks. All were Oscillatoria which do not use N2 EVER.
The heterocyst are required for this process since the enzyme cannot work in
a aerobic environment like that's in a cell with a chloroplast cranking out
all sorts of O2. The heterocyst are very distinct and easy to spot. I have
not found one after looking for many hours in any samples. This genus also
does produce heterocyst...
So if you think low NO3 levels causes BGA, well I'm afraid you are likely to
very mistaken. They need it just like the plants.
Other notes of interest:
No spirogyra was found in any of the hair algae samples. Cladophora is often
what is sometimes referred to as "haystack green algae". It has large
brached straight deep green hairs often in the gravel.
Staghorn appears to be Entermorpha and is a hollow tube shaped structure and
is a generally a marine group.
Large amounts of diatoms even in tanks were you would see none were found in
every sample.
If you have some weird looking algae or brown slimy stuff please email me
off list and send if you wish. I'll try to get to most of it as I can.
It'll be a week or so and I'll have some more info regarding this last
sampling.
Regards,
Tom Barr
The Krib
Plants
Plants