How To Get Rid Of Cyanobacteria In An Aquarium

Imagine looking at your fish tank, feeling amazed by the pretty underwater world you’ve created. But then, you notice something not so nice – cyanobacteria. 

These are like unwanted visitors, often called “blue-green algae,” that can quickly make your aquarium water cloudy and yucky. A lively fish tank, where colorful fish swim in clear water, is wonderful. But the calm and beauty can be spoiled by cyanobacteria, also known as blue-green algae. 

In this complete guide, I’ll talk about why cyanobacteria grow, help you figure out if they’re in your tank, share ways to get rid of cyanobacteria in an aquarium, and give you tips to stop them from coming back. Let’s begin and make sure your fishy home stays peaceful and lovely.

What causes cyanobacteria in aquariums?

Before we start dealing with the cyanobacteria problem, it’s important to understand where it comes from. Cyanobacteria thrive in certain conditions that help them grow. 

If you were giving too much food to your fish and not changing the water often enough. Similar to how too much junk food can be harmful to us, this extra fish food can fill the water with things called nitrates and phosphates. These act like tasty treats for cyanobacteria, creating a perfect environment for them to live in.

Another factor is poor water circulation. If the water doesn’t move much, it becomes still like a pond. In these quiet areas, cyanobacteria can thrive and multiply because they prefer calm waters.

Think of your aquarium as a garden. Some parts receive lots of sunlight, while others are shaded. Cyanobacteria prefer shady spots with less light. It’s like they found a cozy hiding place where they can grow without much competition.

Understanding these reasons can help you prevent cyanobacteria from appearing and causing issues in your aquatic environment.

How do you identify blue-green algae?

It’s important to know how to find blue-green algae so you can act fast. Look for these signs:

  • Slimy, Greenish-Blue Coating: If your aquarium has a slimy, jelly-like layer on things like glass, rocks, and the bottom, it’s a clue that these algae are around and leaving their mark.
  • Musty Smell: Ever been near a pond or swamp? Sometimes, there’s a smell of dirt. If your aquarium starts to smell like this, it could mean these blue-green algae are present.
  • Oxygen Bubbles: Imagine your aquarium is like a soda can. When you shake a soda can and open it, bubbles come out, right? If you disturb these algae, they might release small bubbles, making your water look fizzy.

Recognizing these signs helps you know if these algae are growing too much, so you can take action to stop them before things get worse.

Methods To Get Rid Of Cyanobacteria In An Aquarium

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What are natural methods for eliminating cyanobacteria or blue-green algae?

1. Embrace the Power of Plants

Just like your garden plants need water and sunlight, your aquatic plants crave the same essentials. When you introduce live plants to your tank, they enter into a friendly competition with the algae, vying for the nutrients they both require.

It’s like a friendly contest where the plants emerge victorious, and the algae are left with no choice but to seek a new abode.

2. Tweak the Lighting

Think of the lights in your fish tank like the sun shining underwater. If you change where the light is stronger, you can make it hard for those annoying blue-green algae to grow. It’s like making certain spots sunnier to make it not nice for the algae to stay there.

3. Regular Water Changes

Just as you tidy up your living spaces, your aquarium also requires routine cleaning. When you replace the water, you effectively eliminate some of the algae’s favorite food sources. This action is akin to reducing their sustenance, curbing their ability to grow and multiply.

4. Bring in Helpful Friends

If you’ve got some small pals in your tank, like snails and fish that enjoy eating those pesky algae, you’re in luck.

When you introduce these friendly helpers, they happily gobble up the algae, keeping your underwater home tidy and balanced. It’s sort of like having a tiny team of cleaners that make sure the algae don’t take over your tank.

Removal of Cyanobacteria with Medicine

When cyanobacteria become a big problem, sometimes we need to use chemicals to help:

Using Antibiotics

When blue-green algae become a major issue, you might consider using antibiotics as a solution. Erythromycin, a specific antibiotic, can effectively combat these troublesome algae.

However, keep in mind that using antibiotics should be your final choice due to potential side effects. It’s like using a powerful tool only when absolutely necessary.

How to Prevent Cyanobacteria Problems In An Aquarium?

Here’s how you can keep your aquarium safe from cyanobacteria problems:

1. Feed Your Fish Wisely 

When giving food to your underwater buddies, make sure to give them just the right amount. Too much food can lead to too many nutrients in the water, which cyanobacteria love. So, feed them carefully

2. Get a Good Filter

Think of a filter as your aquarium’s cleaning crew. It takes out the stuff that can make your water dirty and keeps it full of oxygen. A strong filter is like having a super helper to keep your aquarium clean and healthy.

3. Keep Things Tidy

Like tidying up your room, your aquarium needs regular cleaning too. Change some of the water regularly and clean the equipment.

This way, you stop too many nutrients from building up, which could lead to cyanobacteria taking over. Just imagine it as giving your fish a fresh and clean home to live in!


Keeping your aquarium healthy and beautiful requires careful attention, knowledge, and smart thinking. Now that you know why cyanobacteria appear, how to recognize them, and ways to get rid of them, you’re ready to bring back the wonderful colors and life to your aquatic paradise.

By using natural solutions, being a responsible aquarium owner, and preventing problems before they start, you’ll make sure your aquarium stays peaceful and lovely, free from the grip of cyanobacteria. I hope this information is useful to you. Thank you.


Does cyanobacteria hurt fish?

Think of cyanobacteria as sneaky troublemakers. They can release harmful substances that might make fish sick. It’s important to act fast and remove them from your tank to keep your fish safe.

What fish eats cyanobacteria?

Some fish like Siamese algae eaters, certain cichlids, and specific snails enjoy eating cyanobacteria. They help keep it under control in a natural way.

Do water filters remove cyanobacteria?

Water filters are like strainers for your tank. They can catch some cyanobacteria, but they might not catch them all.

It’s like trying to catch sand with a net – some might slip through. To really solve the problem, you’ll need to use other methods along with the filter.

Does UV sterilizer get rid of cyanobacteria?

Think of a UV sterilizer as a special tool that messes up the cyanobacteria’s plans. It messes with how they grow and multiply.

But here’s the secret – it can’t do everything by itself. You have to do other things too, like keeping your tank really clean, to make sure those pesky cyanobacteria don’t return.

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  4. How To Get Rid Of Snails In The Aquarium
  5. How To Fix Bacteria Bloom In Fish Tank