How to control cyanobacteria (Blue-green algae) in an aquarium
March 24, 20201 min read
Cyanobacteria, or blue-green algae (BGA) appears as dark green slime. This algae starts as translucent sheets, often along the substrate, and hugging poorly growing plants. It can form filaments that trail in the current. It is often caused by a combination of deteriorating plants, excess organic waste at substrate level, poor oxygen levels, and low nitrates. BGA is actually a photosynthetic bacteria capable of fixing gaseous nitrogen. In large amounts, it smothers plants and plant growth can stall - giving rise to more issues.
Algae eaters often avoid this algae as it can be toxic.
Unstable or immature tank bio-filter causing bacteria imbalance
Low oxygen or nitrates, coupled with high light
Build up of organic waste & detritus
Dead spots/low flow areas
Small spots can be manually removed or spot dosed with APT Fix.
Improving circulation & oxygenation in affected areas can clear mild cases
Serious outbreaks may require anti-biotics; Erythromycin. This may impact your nitrifying bacteria though. Commercial products such as UltraLife Blue green slime remover and Chemiclean works as well.
Serious outbreaks may be solved by 3-5 day blackout.
Water changes and light substrate vacuum to clear organic debris.
Increase dosage of nitrates if plants are nitrogen starved.
A patch of cynobacteria / blue-green algae (BGA) on substrate, above.
Blue-Green algae appears as a slime across carpet plants above.