How to Get Rid of Black Algae in a Fish Tank

Many people agree that having fish in any room is very relaxing and mood improving. But keeping your fish tank clean and environment stable for ecosystem can be a hurdle and sometimes things go wrong no matter your best intentions. But don’t worry, as most things are fixable and I am here to help you understand what black algae is and how to get rid of it.

The key to beating this, or any other nuisance algae, is to change the conditions in the aquarium with cause it to thrive.

What Is Black Algae?

Black algae in fish tank

Black beard algae is a subtype of red algae, which thrives in high phosphate environments. Sometimes it can appear in greenish or blueish colors. It’s soft to the touch and appears like patches of dark hair, hence the name. It’s very persistent and is often difficult to remove because it has a tendency of returning.

Black beard algae could be a sign that more water changes are needed, possibly with a Gravel cleaning syphon. Or it might be that your tap water contains high levels of phosphate. A simple water test can save a great deal of guesswork and help you tailor a maintenance schedule that suits your aquarium, so you probably want to do this first.

How To Get Rid Of Black Algae

Check Your Tap Water

If you are using tap water for your fish tank, then check if it contains high level of phosphate. In some cities, there are places where old lead plumbing is still being used. And because it is corrosion prone, phosphates are added to the water to prevent lead poisoning. So if you water contains high levels of phosphate, you need to find another source for where to get your water.

This is the most common reason why people get black algae in aquariums.

Dip Aquarium Decorations in Hydrogen Peroxide

Regular over the counter peroxide (3%) can be used for this. Bear in mind that the more gentle plants, like Japanese Moss balls, may get hurt by this method. Most likely, it won’t kill them, but they will struggle. If you only have plastic plants in your fish tank you can even use bleach in a 1 to 20 ratio.

Soak your decorations that are visibly affected by the black algae for 2 to 3 minutes then rinse them very thoroughly. Using peroxide, you can put your plants, rocks and other decorations back into the fish tank immediately.

Give Extra Effort Cleaning Your Fish Tank

First, make sure you know how to properly clean a fish tank to avoid any basic mistakes.

Phosphates are a byproduct of almost everything that decays in your aquarium. This includes leftover food, plant and algae decay and fish waste. So make sure you clean your fish tank thoroughly, use a syphon to clean any leftovers and waste that resides at the bottom of the aquarium.

Also clean your filters regularly, as they can hold enough of the bad stuff that will eventually spike phosphate levels in your fish tank.

Make sure that you lighting is working as supposed to and do not leave it on longer than actually necessary.

Add Black Algae Eating Fish To Your Fish Tank

Few aquatic creatures will actually eat black algae, but, luckily, there are some. One of the best black algae eating fish is Siamese Flying Fox Crossocheilus siamensis.

For this method to be most effective, you want to inject CO2 into your fish tank (Only if you have real plants). In a fish tank low on carbon dioxide, the algae will be stiffer to the touch and won’t be an appealing appetizer even for the Siamese Algae Eater. By raising the CO2 levels in your fish tank, your aquatic plants will consume more nutrients, weakening the black beard algae. When weakened, the black beard algae will become a great snack for the Siamese Algae Eaters and some other algae eaters as well.

Fish that will eat black algae when it is weakened:

  • Siamese Flying Fox (Will eat it even if it is not very weak)
  • Black Molly
  • Chinese Algae Eater
  • Twig catfish

Good luck getting rid of the nasty black algae infestation!