How to get Rid of Blue-Green Algae In Aquariums

How to Get Rid of Blue-Green Algae in Aquariums

Is your aquarium being overrun by a blue-green slime? Or is there a strange smell coming from your fish tank and you can’t find the source? An outbreak of blue-green alga might be the problem. We will discuss the causes and how to eliminate blue-green alga.


What is Blue-Green Algae?

Blue-green algae (BGA) is not actually an algae but rather a cyanobacteria – a very diverse and resilient group of bacteria that uses photosynthesis like plants. It is most well-known for its bright blue-green color in freshwater aquariums. However, it can also be found in black, brown, and even red. You might see it as a tiny bit of green algae. It eventually grows into thick slime, covering your gravel and decorations. While cyanobacteria in aquariums does not usually harm fish, it can potentially kill your plants if their leaves are covered and can no longer photosynthesize light.

Another way to identify blue-green algae is by its distinct odor. The smell can be described as foul, earthy, musty and swampy by many people. Once you have learned to recognize the scent, it’s possible to detect cyanobacteria up to two weeks before it’s even visible in the fish tank.

Blue-green algae is actually a type of photosynthetic bacteria that comes in blue, green, brown, black, and red colors.


What Causes Cyanobacteria in Aquariums?

Many studies have been done to figure out what causes cyanobacteria blooms, since they can have a deadly impact on the environment. There are not yet any definitive answers, but they often occur in warm, slow moving, and nutrient rich bodies of water. In the aquarium hobby, we have frequently seen blue-green algae pop up wherever organic waste has a chance to stagnate in certain areas of a fish tank. If:

– The current in the fish tank is too slow – Hardscape is blocking off a corner of the aquarium that also gets exposed to constant light – The substrate is collecting debris because the gravel hasn’t been vacuumed in a while and there are no animals to churn it

How can I naturally get rid of blue-green algae?

Based on these possible causes, the first step is to manually remove as much of the slime as possible using a siphon, toothbrush, or algae scraper. Your clean-up crew will not be able to help you because animals don’t like blue-green algae. Remove any excess nutrients by doing water changes more frequently, cleaning the filter regularly, and reducing the amount of fish or food going into the aquarium (if overfeeding is a problem). You can improve the water flow by adding a powerhead or a stronger filter.

Photosynthesis is used by Cyanobacteria to produce energy. To starve the colony, some recommend turning off aquarium lighting for three to seven consecutive days. However, this method can end up harming your plants (which also use photosynthesis) or causing spats among the fish. Plus, the blue-green algae often returns within a few weeks.

Cyanobacteria: Can Medicine Treat It?

People often have difficulty dealing with stubborn bacteria. Fortunately, it is weak against an antibiotic called Erythromycin. This medicine is safe for fish, plants, and invertebrates, and it will not harm the beneficial bacteria in your aquarium. Fritz Slime Out is an aquarium treatment that treats cyanobacteria. It does not raise phosphate levels.

You can begin treatment by scraping off as much blue-green alga as possible. After cleaning the substrate, fill the tank with Slime Out (1 packet per 25gallons). Let the aquarium rest for 48 hours before performing a 25% water change. Add an air stone or other filtration that agitates the water surface to help ensure the fish have enough oxygen during the treatment. The earlier you treat the outbreak, the easier it is to eradicate. If the blue-green algae is very thick and widespread, you may need to repeat the treatment several times to completely remove the colony.

If you address the underlying causes of cyanobacteria and treat it with Slime Out, you should have no problems getting rid of it in your fish tank. Our complete guide on how to eliminate the top 6 types in freshwater aquariums is available here.