How to get Rid of Blue-Green Algae In Aquariums

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? Blue-green algae might be a problem. In this article, we discuss the causes of blue-green algae and how to get rid of it once and for all.


What is Blue-Green Algae?

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. Although it is best known for its vibrant blue-green color in freshwater aquariums it can also be found as a black, brown, or red. You may see it start off as a little spot of green algae that eventually grows into a thick slime stretched over your gravel, decorations, and plants. 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 alga is a type photosynthetic bacteria. It comes in different colors, including red, brown, black and green.


What is Cyanobacteria?

Since cyanobacteria can have a devastating impact on the environment, many studies have been conducted to identify their causes. While there are no definitive answers yet, they commonly 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 do I get rid of blue-green algae naturally?

These possible causes are the basis for the first step: manually remove as much slime as you can using a siphon or toothbrush. Blue-green algae is not something animals like so your clean-up crew won’t be much help. 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 increase the water flow by using a stronger filters, adding a powerful head, or moving equipment and decorations around the tank.

Because Cyanobacteria relies on photosynthesis to generate energy, many people recommend that the aquarium lighting be turned off for at least three to seven days in order to starve the colony. However, this method can end up harming your plants (which also use photosynthesis) or causing spats among the fish. The blue-green algae can also return within a few days.

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 our favorite, as it’s formulated to reduce cyanobacteria and 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 vacuuming the substrate and refilling the tank, add one full dose of Slime Out (which is 1 packet per 25 gallons of water), and let the aquarium sit for 48 hours before doing 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 easier it is for the outbreak to be treated, the earlier it can be dealt with. To completely eradicate the colony, it may be necessary to repeat the treatment if the blue-green alga is extremely thick or widespread.

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.