How to Remove Beard Algae from an Aquarium

Beard algae (also called brush algae) belong to the red algae family and grow on the edges of plant leaves and on the edges of almost all hard surfaces. It consists of very thin strands or clusters that grow into dense patches that resemble a dirty green beard, hence the name. It can also be bright green, teal to dark green. It’s soft, smooth, and grows quickly, but still clings tenaciously to plants and isn’t easy to remove by hand. It is eaten by only a few species of fish, notably the Florida sailfish and the Siamese seaweed eater (Crossocheilus siamensis).

Causes of Beard Algae

Perhaps the number one reason is unstable or low levels of carbon dioxide. When carbon dioxide is unstable, plants cannot use the available fertilizer and light for photosynthesis, an environment that is hospitable to bearded algae. In this case, supplemental carbon dioxide may be required.

Beard algae most commonly enter the tank of contaminated plants. However, even a small free-floating line in a bag with fish is enough to start its growth in your aquarium.

Treatment for Beard Algae

Affected plants can be soaked in a 10% bleach solution for two to three minutes to kill any algae on them. (Never pour bleach into the aquarium!) Completely remove severely affected leaves. Bleaching rock, gravel, and any other items that exhibit algal growth. Stock the tank with Siamese algae (Crossocheilus siamensis).

Illustration: The Spruce/Alison Czinkota

notes: Be sure to buy the right fingerlings, as many are sold under the name Siamese Algae Eaters. Other species of fish do not eat algae. If other options fail, treat with copper according to manufacturer’s instructions. However, copper can adversely affect certain plants and fish and should be used with caution.

Follow a rigorous weekly tank maintenance schedule. Weekly water changes are necessary to replenish lost minerals and stabilize pH to avoid an overly acidic environment. Continue to clean debris and do not overfeed.

When bearded algae is attached to the tank, it is difficult to separate it from the gravel, glass and silicon seams. It takes a lot of elbow grease to remove it from hard surfaces. Try a toothbrush, magnetic scraper or razor, and a spray treatment like Seachem Excel or Metricide.

Beard Algae Prevention

Prevention is the best course of action. Once bearded algae begins to grow, it will quickly cover everything that is not moving in the aquarium. On plants, it can block light and stop photosynthesis, causing the plant to die.

To prevent algae from entering the tank through the fish, isolate new fish for at least two days. When placing them in the tank, scoop up the net rather than pour them out of the bag so the water in the bag doesn’t get into your tank. Prophylactically soak newly purchased plants in a 10% bleach solution for two to three minutes to kill any algae on them. Also, buy plants and fish from a well-known local fish store.


How to Remove Beard Algae from an Aquarium
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