How to get Rid of Blue-Green Algae In Aquariums

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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? You might be dealing with an outbreak of blue-green algae. This article will explain the causes of blue green algae and how you can eliminate it permanently.


What is Blue-Green Algaee?

Blue-green alga (BGA) does not exist as an actual algae. It is actually a cyanobacteria, a group of bacteria that uses photosynthetics like plants. In freshwater aquariums, it’s known for its vivid blue-green color, but it can also appear in shades of brown, black, or even red. It may appear as a small spot of green algae, but it eventually becomes a thick slime that covers your gravel, decorations, plants, and other items. 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.

The distinctive smell of blue-green alga can be used to identify it. 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

There have been many studies to determine what causes cyanobacteria blossoms. They can have devastating effects 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. This could happen 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 won’t be of much help, since animals don’t like the taste of 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 increase the water flow by using a stronger filters, adding a powerful head, or moving equipment and decorations around the tank.

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.

Can I Treat Cyanobacteria with Medicine?

This stubborn bacteria is a problem for many people. However, it is extremely resistant to an antibiotic called erythromycin. This medicine is safe for fish, plants, and invertebrates, and it will not harm the beneficial bacteria in your aquarium. We personally like to use Fritz Slime Out, which is formulated to treat cyanobacteria without raising phosphate levels in the aquarium.

Start treatment by removing as much blue-green algae from the tank as you can and then using a siphon to remove it. 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. It is easier to eliminate an outbreak if you act quickly. You may have to repeat the treatment multiple times if the blue green algae 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. If you’re struggling with another type of algae, check out our full guide on how to fight the top 6 types of algae in freshwater aquariums: