How to Get Rid of Blue-Green Algae in Aquariums

Do you have a mysterious, blue-green slime taking over your aquarium? Or is there a strange smell coming from your fish tank and you can’t find the source? A possible outbreak of blue green algae could be happening. This article will address the causes of bluegreen algae and the best ways to eradicate it.

What is Blue-Green Algaee and How Does It Work?

Blue-green algae (BGA), isn’t actually an algae, but a cyanobacteria. This is a diverse and resilient strain of bacteria that uses photosynthesis to grow plants. It’s most commonly found in freshwater aquariums as a vivid blue-green algae. But, it can also come in other colors such as brown, black or 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.

Blue-green algae can also be identified by its distinctive odor. It can smell foul, musty or swampy. 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?

Since cyanobacteria can have a devastating impact on the environment, many studies have been conducted to identify their causes. 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 manually removing as much slime from the area as possible with a siphon, toothbrush or algae scraper. The blue-green alga isn’t something that animals will enjoy eating so it won’t be helpful to call in a clean-up crew. 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.

Cyanobacteria uses photosynthesis to create energy, so some people suggest turning off the aquarium lighting for three to seven days to starve out the colony. However, this method can end up harming your plants (which also use photosynthesis) or causing spats among the fish. In addition, the blue-green chlorophyll often returns within a few hours.

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 and does not increase phosphate levels.

To begin treatment, scrub off as much of the blue-green algae as possible and remove it with a siphon. After cleaning the aquarium, fill it with Slime Out (1 packet per 25gallons). The aquarium should be left to sit for 48 hours. Add an air stone or other filtration that agitates the water surface to help ensure the fish have enough oxygen during the treatment. It is easier to eliminate an outbreak if you act quickly. You may have to repeat the treatment multiple times if the colony is large and thick.

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. Check out our guide to the top 6 types and how to eliminate them in freshwater aquariums.