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Control of Red Algae in the Freshwater Aquarium

by nfrank-at-nando.net (Neil Frank)
Date: Sat, 18 May 96

Because there has been a bit of discussion recently on 'beard' algae (both on this list and in the May issue of FAMA), I thought I would share an article that I have been working on. Much of this information has appeared in TAG or has been bantered about on the net, but I don't think it can all be found in one place.

Introduction

Among all the algae that can invade and gain a foothold in freshwater aquaria, red algae from the division Rhytophyta, can be the most frustrating to the hobbyist. This furry, thread-like flora attaches to various aquarium surfaces including the edges of plant leaves, filter tubes and even gravel. It may have many colors (purple, gray-green, black) and resembles beard hair or fur. In the aquarium literature, this nuisance is often called beard or brush algae. Baensch Aquarium Atlas' illustrate and talk about three forms. The long thread variety is called beard algae (once misprinted as bear algae), the shorter thread type is called brush algae; and a third type is described as having very short threads and forms dark roundish spots. While most algae from this family are actually found in marine or brackish water environments, there are a few species that inhabit freshwater (including the genera Audouinella). In nature, these epiphytic freshwater red algae are found in fast moving streams which provide a constant, but perhaps low concentration supply of nutrients including CO₂. They also have the ability to attach tenaciously to all objects which makes them well suited to the moving water habitat. Unfortunately, they cannot be easily scraped or pulled from objects, thereby adding to the difficulty of their removal from the aquarium. In fact, when attempting to remove from plant leaves, the aquarist or even fishes may tear the leaf in the process. On the positive side, some hobbyists find this algae an interesting and welcome addition to their tanks. It may offer a special charm to driftwood or rocks, especially with the undulating movement created by the downwash of a filter outlet or powerhead.

The red algae is often the topic of discussion in aquarium literature. In the May 1996 issue of FAMA, four separate articles mention it! In the lead article, Liisa Sarakontu and I talk about the Siamese Algae Eater (Crossocheilus siamensis), perhaps the only fish known to effectively eat and essentially eliminate this algae from the freshwater aquarium. Then Peter Lewis reports on this very same fact in his month column on fish trivia. Third, Simon Ellis presents "Its a Jungle in There" and mentions his unsuccessful battle with red algae. Finally, in the freshwater Q&A column, Simon appears again to ask Owen Jeffries: "How do I prevent a recurrence of the black bush [brush] algae." Owen, however, falls short of answering his question. Fortunately for Simon, there are many effective cures for the red algae plague. Here is the rest of the story.

Causes for Red Algae in the Aquarium

The most likely reason for red algae is introduction of contaminated plants or a bag of fish from a store tank with red algae. This can come in as some small filaments floating in the water, as water born spores or perhaps in the digestive tract of fishes. Once deposited into a suitable aquarium environment, they may become established. It is evident from the picture of Simon's lush planted aquarium in the May FAMA that this was the case.

Unlike Jeffries, I do not believe that soil used under the substrate is a likely source of red algae. I have used soil in some of my planted tanks for many years and never saw red algae in these tanks, even before I found the Siamese Algae Eater. I am also not aware of this problem with many other aquatic gardeners who believe that the iron, manganese and other nutrients derivable from soil can be very helpful for a plant tank, provided that all other conditions are correct and the plant density is sufficient. Perhaps this route of entry is plausible if the soil is was taken from a river bank or if aquatic sediment is used. Nevertheless, deposited red algae will benefit from the extra nutrients which can also originate from soils. If a complete set of nutrients are available in the water column from whatever source, algae will thrive.

Simon also wonders if very high light levels and iron levels may be the key to prevention. His question appears to be rhetorical because both of these parameters are important indicators of plant and algae growing conditions in the aquarium. Sufficient light is need for good plant growth and generally speaking the rate will increase with higher intensity. Actively growing plants will also soak up nutrients from the water column helping to starve algae. While rooted plants can derive nutrients from the substrate, algae basically get their food from the water. If nutrients concentrations are reduced in the water column, the algae will suffer.

Approaches for Eliminating Red Algae

Eliminate it before it enters the aquarium.

First, the aquarist can attempt to avoid introducing red algae into an uncontaminated aquarium. This is most important if red algae is seen in the local area, say, in the local aquarium shops. Contamination from transferred plants is likely, even if the algae isn't clearly visible. In these situations, a suggested approach is to 'disinfect' the plants to kill the red algae. It may also be helpful to avoid using any water from an aquarium shop (e.g. acclimate new fishes in a bucket) and quarantee new fish for a few days until they clear their digestive system.

Removing infected leaves is another good idea. In any event, removing some older leaves is often the suggested protocol to reduce the shock of transplanting. With cases where slow growing plants like Anubias have been exposed, however, all leaves may be covered and it becomes impractical to remove the affected parts.

Although what I am about to suggest sounds a bit drastic or potentially harmful, it is actually quite safe and very effective. It also avoids the necessity to remove any leaves. The suggested procedure involves a 2 to 3 minute disinfection bath in diluted household bleach (1 part bleach to 19 parts water). You can use the name brand products or the generic. Just get the ordinary bleach and do not get the variety with the added lemon scent. Place the plant in the solution (including one that is totally covered with algae) and gently circulate the bleach solution to ensure good coverage. The fine leaf plants are the most sensitive and should only get 2 minutes, while the broad leaf varieties including Java fern, sword plants and Anubias can take the full 3 minutes. Next, give them an immediate rinse in clean water. I usually have a bucket with clean water ready and I simply transfer the plant to the new container and leave it there for a few seconds. The previously touch algae is now dead, visible pieces can be more easily removed by rubbing the leaves between your fingers and the plants are now ready to go into their new home.

Some plants will later loose their leaves, but when placed into a suitable environment (good light, nutrients, etc), the plants will quickly recover and soon take off. As a bonus, the bleach treatment (but perhaps with more than 3 minutes immersion) will also eliminate the green hair algae (Pithophora, Cladophora, Oedogonium, etc). Plants like swords, crypts and Anubias can take 4 minutes of the bleach treatment without too much damage. The tough tectured hair algae can be very resisitent and really need 4 minutes. Fortunately, stem plants that can't take 4 minutes are able to outgrow cladophora, which usually attaches to old parts and doesn't seem to spread to the young parts very quickly. As many of us know, these algae can be just as big a nuisance down the road.

Bleach can also be used to remove algae from other aquarium objects including rocks, filter parts and even gravel. Of course this would be done outside the tank. Rinse everything very well and be sure to remove all traces of bleach. Your nose will be a good judge. Extra rinsing and even air drying is suggested for porous or large surface area items like clay pots.

Provide trace elements to the plants and deprive the algae.

If one or more plant nutrients are substantially reduced or completely eliminated from the water, then the algae will fail. This can be accomplished by managing iron which is one of the most important trace nutrients.

Iron can be provided to the aquarium in several ways -- thru feeding and subsequent mineralization of detritus; with soil or laterite in the substrate, some from new water introduced with water changes, and with the addition of plant fertilizers. Sufficient iron is desirable, but too much is bad. While iron is needed for good growth of all plants, including algae, excess amounts will merely be extra food for algae and help it to thrive. Iron is often a limiting plant nutrient and it can be an indicator of the concentration of other needed trace nutrients.

Most iron in the aquarium (e.g. from decomposing organic matter, mineralized detritus or from added tap water) will be bound to oxygen or organic matter and will be less accessible to algae. Digested iron will be excreted as feces and deposit in the substrate. The same is true for any iron oxidizes, as contained in soils or laterite.

Limit the amount of added soluble, iron bearing aquarium plant fertilizer. Rooted plants can derive iron from the substrate in addition to getting it from the water. However, algae (and floating plants) can only get it from the water. So, one strategy is to reduce the amount of added iron. Many fertilizers contain a chelated form of iron which is designed to keep the iron in solution. The recommended dose is often designed to produce a concentration of approximately 0.10 ppm and may be based on daily or weekly additions. Unfortunately, label suggestions are based on some typical condition which may not be ideal for your situation. Depending on the nutrient uptake based on density of plants, their general health, growth rates as well as the existing reservoir of iron in the aquarium, the target concentration may be too high. Therefore, some trial and error may be needed to determine the correct dosage for your situation. I also note that the iron concentration is also an indicator of the amount of a variety of other trace element nutrients used by both higher plants and algae.
Add iron directly to the substrate. A final way to reduce iron in the substrate is to not intentionally add any iron bearing fertilizers to the water. However, iron must still be made available to the plants. The latter reason is why good plant growth can occur in an established tank but not in some newly established ones. Fish excretions will supply most other nutrients, so many aquarist can have virtually algae free plant tanks with good lighting and regular feeding of the fish. In all of these cases, the insoluble iron from the soil or from mineralized detritus can be chemically modified (reduced) in the oxygen free, anaerobic areas of the substrate and become accessible to the plants through their roots. Small amounts of iron and other trace elements in the water will still be soaked up by the plants, thereby helping to starve the algae. With this stategy, supplemental additions of iron may become necessary when the plants are well established and the roots totally fill the substrate. Then it becomes difficult for the plants to get their iron from this source. Hopefully, by this time all the algae problems are under control.

Manage the rate of nutrient uptake.

This is another way to control excess iron and other water soluble nutrients. This is where lighting and plant density come in -- generally the more light, the faster the plant growth and with more plants, the faster the nutrient concentrations are depleted. Sufficient light is need for good plant growth and generally speaking, growth will increase with more intense light. Because actively growing plants will soak up nutrients from the water column, this helps to starve algae. Although it is also a good idea to avoid introducing excess nutrients, a heavily planted tank will make it difficult for any extra to remain around for long. Regular water changes are also important to avoid nutrient buildups.

In heavily planted tanks with few fishes or ones that are fed lightly, it may be possible to develop a nitrogen deficiency. This will cause plant growth to slow down and allow some algae to start to get the upper hand. Perhaps this situation can also benefit red algae.When this occurs, nitrogen supplements may be needed to re-establish the nutrient balance and permit plants to outcompete algae.

Use lots of heathy plants to help get things off to a good start.

It is important to plant heavily to permit plants to outcompete algae, especially in a new setup. It is even more important to use healthy plants. Sometimes plants are weakened during transit from the grower to the aquarist, so newly purchased plants may take a while to become acclimated. They will not be growing quickly and soaking up nutrients if they are not in good condition. It is best to know the source of your plants and get them from the actual grower (perhaps yourself) rather than through a transhipper. I also like to obtain them when they first arrive at the aquarium shop before they have a chance to pick up any new algae or have their roots damaged from an additional planting.

Consider CO2.

Another nutrient which may be related to the sustenance of red algae is inorganic carbon. This exists in the aquarium as dissolved CO₂, bicarbonate or carbonates. The equilibrium of these carbon species depend on pH. Free CO₂ becomes available at pH less than 8.0 and predominates when pH is less than 6.5. In my experience, I have only seen red algae in low alkalinity, low pH conditions. Tanks with calcareous substrates will push the carbonate equilibrium from CO₂ to HCO₃^- and red algae seem to diminish. Accordingly, I used to see beard and brush algae in my South American cichlid tanks, but never in the Tanganyikan tanks with their crushed coral substrate. It seems that red algae may be among those algae and water plants that can only utilize free CO₂. On the other hand, some books suggest that adding CO₂ will help eliminate red algae. Although this first appears to be a contradiction to my hypothesis, I believe this method is effective because CO₂ injection helps to increase the rate of plant growth. As mentioned earlier, with a large density of plants and bright light, the plants will suck up dissolved nutrients and cause algae to subside. The same effect can be accomplished by CO₂ obtained from aquatic organisms or decomposition of organic matter. Hydrogen peroxide and enzymes are also said to control algae. I believe this is due to a similar effect -- increased bacterial growth, which provides the potential benefit of increasing CO₂ concentrations.

Utilize algae eaters.

The next major strategy for algae control involves algae eating. First and foremost is the Siamese algae Eater (Crossocheilus siamensis), perhaps the only known fish to eat red algae. As mentioned earlier this cyprinidae and its look-a-likes was the subject of the lead article in the May issue of FAMA and was also featured in the April issue of Aquarium Fish Magazine. As with all algae eating fishes, it is best to introduce them into an aquarium before red algae becomes established -- preferably, when the tank is first set up. Feeding should be minimized during this stage so that the SAE and other algae eaters will be trained to seek out algae as their source of nourishment. In an established tank, a small school of these fish will also help out and can quickly eliminate mature red algae from your tank. A second animal in the arena of hair algae control are shrimps. The Yumato-numa-ebi, the Japanese marsh shrimp (Caridina japonica) is used almost exclusively in Japan and Taiwan for algae control. These creatures which are native to Asian waters are mentioned in Amano's great book Nature Aquarium World and are a more colorful alternative to our native glass or grass shrimp. Amano says the Yumato numa ebi is the best algae eater. Caridina and similar Neocaridina species are not yet available in the U.S. Our fresh water shrimps are called glass or grass shrimps (Palaeomonetes sp.). They are also native to Europe. Glass shrimps can be found in aquarium shops and fisherman's bait stores. I have used both the Yumato-numa-ebi and glass shrimps and can personally report success with hair algae. To be effective, the shrimps must be used in large numbers, not allowed to eat preferred fish food and obviously can't be used in tanks with certain hungry fishes. When needed to control algae in such tanks, add lots of shrimps at night. They will work on the algae while the fish sleep and then the fish can have a snack in the morning. If used in a tank where the only source of food is plants and algae, they may start on the plants when detritus and other food supplies disappear.

Use Chemical controls.

Copper will kill red algae. However, I only suggest this measure as a treatment of last resort. Although I first discussed algicides in 1986/7, these chemicals have been used to control algae for a long time. Unlike other algicides sold for aquarium use (e.g. simazine), copper will kill red algae. Unfortunately, it will also harm some aquarium plants (e.g. Myriophyllum and Vallisneria), so it should be used with caution. However, the treatment will not harm many desirable aquatic plants including Echinodorus (sword plants.), Cryptocoryne (crypts), Anubias, Microsorum (Java Fern) and many others. The major advantage to the copper treatment is that the tanks does not have to be dismantled and disinfected -- the plants, rocks, gravel can be all left in place. In addition, some plants (crypts) actually seem to benefit from the slug of copper while many other sensitive algae succumb to the treatment. The only thing that should generally be removed are the fishes.

To effect the treatment, copper concentration should be maintained at 0.5 ppm for 7-10 days. The copper can be added as copper sulfate solution or as other copper compounds. There are several aquarium products which can be used including the medicines designed to kill Oodinium, a parasitic algae. A copper test kit is needed to be sure the needed concentration levels are up and more copper may be needed after the first day because plants and other organics will absorb or bind with the chemical. To reduce dissolved organics, it can also help to first pre-filter the water with carbon or do a large water change prior to adding copper in order to improve the effectiveness of the treatment. In general, the fishes should be removed and only returned after the copper concentration is again below detection limits. This is especially important for cyprinids and live bearers which are particularly sensitive to copper. Same is true for snails and other invertebrates. Some fishes including cichlids are relatively tolerant to copper and may be allowed to remain in the aquarium if difficult to net out.

Summary

I have presented several methods for preventing or eliminating red algae. The principle methods are: pre-treatment of plants with bleach, reduction of water column nutrients, algae eating animals and copper algicide. Although this provides the rest of the (current) story, it may not be my final word!

Neil Frank, TAG editor    Aquatic Gardeners Association    Raleigh, NC USA



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