How to Get Rid of Black Algae in a Fish Tank?

You’ve noticed the black or blue-green spots of fuzz clinging to everything in your aquarium. 

…Or maybe they’ve already grown to look like a beard or brush-like.

You’ve also noticed how rapidly the spots spread, and trying to get rid of them only works for a short while before they come back up again. 

It’s become a menace because the more it spreads, the more light it blocks, posing a danger to your aquatic plants. 

But how did BBA get into your fish tank in the first place?

The black beard or brush algae (BBA) from the red algae family appears in a fish tank because of an imbalance in carbon dioxide, light, nutrients, and oxygen. 

So, if your fish tank has too much light, and low CO2 levels and nutrients, it provides the perfect conditions for black beard algae to grow.  

What’s more, poor water circulation in the tank also creates an excellent environment for black algae growth. 

So, how do you remove black beard algae from your fish tank once and for all?

Step #1: Scrape Off Algae from Decor and Glass

Remove algae from artificial plants and glass using an algae brush or the Magic Eraser from Mr. Clean.

Scraping off black algae from the aquarium glass and plastic decor helps to remove all the loosely hanging algae.

Also, trim infected live plants to reduce the spread of the black beard algae in the aquarium.

Step #2: Perform a Water Change

Change the tank water to remove all the dead BBA you scraped off in step one. 

Now, doing a drastic water change will potentially kill your fish. So, instead, do a partial water change and use a gravel vacuum to suck up the debris.

When doing water changes, confirm that the freshwater you’re adding doesn’t have any form of phosphate in it using a phosphate test kit. Why? Because phosphates provide an ideal environment for black beard algae to grow.

The recommended phosphate level in water is 0.5 ppm or less. A level above 1 ppm will create a breeding ground for black algae.

Most tap water has high phosphate levels.

So, keep off tap water and find an alternative water source like purified or reverse osmosis water (RO water) instead. 

Now, if you choose to use RO water, remineralize it by adding:

  • A combination of baking soda, calcium chloride, and mineral salt or
  • A sulfate-free remineralizer like Seachem Flourish Excel

Alternatively, buy a filter media that absorbs phosphate like the poly filter or combination carbon-phosphate remover. 

You could also thoroughly clean your current filter to remove all dirt like dead plant parts and fish waste

aquarium filter

Otherwise, the dirt will clog the filter and produce phosphate over time, which promotes the growth of black beard algae.

Also, clean the gravel to remove any leftover food because leftover food acts as a fertilizer for black algae.

The best way to clean the gravel is to use a gravel vacuum to turn over gravel substrate, depriving it of light and killing the algae in your aquarium.

This step should clear most of the algae, but if it doesn’t, move to the next step.

Step #3: Blackout the Aquarium

Black beard algae need light to flourish. Therefore, killing the source of light will hinder the algae from growing, causing them to die.

So, completely blackout your aquarium for a maximum of seven days from both the natural (sunlight) and the artificial (aquarium lights) light for the algae to die. 

Now, to totally blackout the aquarium from sunlight, wrap it well with a garbage bin bag or black wrapping foil.

You can also use thick cardboard to block out sunlight; just make sure that it covers the aquarium edges to completely blackout light.

During this blackout period, don’t peep into the tank to try to feed the fish or fertilize the live plants. Instead, do this an hour before the blackout starts. 

Since most aquarium plants don’t require as much light as the algae for photosynthesis, your plants will be safe throughout the blackout. 

The only evidence you’ll have that they went through the blackout period will be their light-deprived leaves, which will be yellowish. But with some light (after the blackout period), they should be back to normal.

Also, switch off CO2 for the whole duration and add an air pump to provide more oxygen to the tank, which your fish and plants will need throughout the blackout period.

Once the blackout period ends, remove the cover and perform a water change to eliminate all the dead black beard algae. 

If there are still some stubborn algae that just doesn’t seem to go away, especially those that cling to plants, then move on to the next step.

Step #4: Soak Affected Decor and Tank in Hydrogen Peroxide

Buy 3% hydrogen peroxide from any supermarket or pharmacy, then soak your plants in it to kill the black beard algae.

Here’s how long and what measures you should use when soaking your aquarium decorations.

DecorTimePeroxide to water ratio
Live plants3 minutes1:3
Artificial plants2 minutes1:20

After soaking, rinse the plants thoroughly with running water to get rid of any trace of peroxide. 

Then soak the fish tank in 10–30 ml of peroxide per 50 liters or 15 gallons of water once a day for 3 days. You’ll notice that the black algae (BBA) starts to wither and die.

The best part is that the dead algae leave no residue behind. 

Pro tip: Take out the fish from the tank when soaking to avoid hurting them.

After soaking the fish tank, perform a 50% water change.

Although most people swear by this method, some black algae can be extremely stubborn and difficult to get off. If this is the case for you, then…

Step #5: Introduce Black Algae Eaters in the Fish Tank

For some aquatic animals like the Amano shrimp and siamese algae eater, black beard algae are the preferred source of food.

For others, it’s not the first choice, but they do a great job at getting rid of it.

Here are some algae-eating aquatic animals.

Fish that Eat Algae

Fish will eat black beard algae, but it has to be soft enough for consumption.

Now, black beard algae are soft to the touch, but dosing them with hydrogen peroxide will make it softer for the fish to eat.

Here are some fish that’ll help you get rid of black beard algae.

  • Black molly
  • Twig catfish
  • Rubber lipped pleco
  • American flagfish
  • Siamese algae eater  
  • Pygmy suckermouth
  • Rose barb 
  • Flying fox


Snails are the most popular algae eaters. However, not all of them enjoy feeding on black beard algae. 

The only snails that consume black algae are the Nerite snails. But they’ll only ingest it if it’s dead.

Zebra Nerite Snail (Neritina_natalensis_sp._zebra)

The only caveat to having snails in your fish tank is how much they excrete, which, if not controlled, leads to an ammonia spike.

The ammonia spike then causes a whole new problem–-your fish dying.

To avoid this, the snails need partners that’ll clean up their waste while clearing out the black algae. Enter…  


Shrimps feed on live black beard algae and will consume it faster than both the snails and fish.

What’s more, the shrimps clean up the snails’ waste that may infect the tank with phosphate that could damage your fish.

The shrimps gain from eating snail poop because it has beneficial bacteria that help their digestive system.

The shrimp that commonly eats black algae is the Amano shrimp.

Note: Be careful when introducing shrimps in the aquarium because they don’t live well with fish like goldfish, loaches, or large rainbowfish. 

However, if you have fish like guppies, Ember Tetras, or Bristlenose Pleco, then you can comfortably add shrimps to your aquarium because they’ll live together peacefully.

Take Control of the Black Beard Algae Problem

Black beard algae can be a nuisance when trying to remove it if you don’t address the root cause because it keeps coming back. 

So, change the aquarium water, ensure it’s phosphate-free, clean up the filter to get rid of the dirt that could act as a catalyst for the algae’s growth, and blackout the tank to block out light that helps it grow.

Furthermore, other methods like scrapping the glass and decor, soaking the aquarium and plants in hydrogen peroxide, and introducing algae eaters like the Siamese Algae Eaters will get rid of algae fast.

Don’t let any type of algae, not even the black beard algae, suck out the joy of keeping a freshwater aquarium. Use the above process to get rid of black algae completely.

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