Does UV Light Kill Black Beard Algae? {Is UV The Answer?}

Black beard algae grows when the tank you are managing is imbalanced. Does UV light kill Black Beard Algae?

I have a UV sterilizer and I have tried using it to kill different forms of algae with some success and some failures as well.

Find out what happened when I used UV light for Black Beard Algae in this article.

Does UV Light Kill Black Beard Algae?

No. UV light does not kill black beard algae which is a fuzzy red algae that can inhabit freshwater tanks. Since black beard algae is technically a red algae, UV light has no significant effect.

How to prevent black beard algae from returning or establishing itself in your tank in the first place involves more effort and the use of:

  • Algae eaters
  • Gravel vacuum
  • Live plants
  • Phosphate Remover
  • Manual cleaning (toothbrush)
  • Hydrogen peroxide (or Excel)
  • Increased CO2 levels

Does UV Light Kill Black Beard Algae

What Does UV Light Do For Aquariums?

UV lights are effective against phytoplankton, which are algae too small to see, as well as many kinds of green algae. Ultraviolet lights are often used to sterilize aquarium tanks in order to kill unwanted bacteria and algae.

It doesn’t kill beneficial bacteria or make your fish sick. It will not save a dying fish however.  The UV sterilizer or ultra-violet lights will kill single cell organisms.

UV light is efficient at altering or damaging its DNA. It doesn’t work well on red algae or black beard algae.

What Kills Black Beard Algae?

Black beard algae can be difficult to get rid of because it can get into the smallest holes and cracks. If you don’t eliminate all of it, black beard algae will return no matter how small of a piece gets left behind.

4 Ways To Eradicate Black Beard Algae:

  1. Hydrogen Peroxide Bath
  2. Hot Water Bath
  3. Algae Eaters
  4. Manual Cleaning

Hydrogen Peroxide Bath

One of the most common ways involves a hydrogen peroxide bath. Remove all infected décor from the tank and soak it in hydrogen peroxide to completely kill the algae.

Hot Water Bath

Another method that is slightly less effective but does not involve chemicals, is placing infected decorations in a boiling hot water bath.

Algae Eaters

If you want to go a more natural route, you can use biological black beard algae elimination methods by introducing fish or invertebrates that eat the algae.

Amano shrimp and nerite snails are great for algae clean up and can get into the hard to reach spaces that the black beard algae tend to inhabit.

There are also a variety of fish species that are effective at eradicating black beard algae such as:

  • Florida flag fish
  • Chinese algae eaters
  • Goodeids
  • Flying foxes
  • Rubber lip plecos
  • Golden algae eaters
  • Siamese algae eaters

Manual Cleaning

When all else fails or you see the hardest to remove spots, it’s time to roll up your sleeves and grab a toothbrush. I use one from the hardware store with stronger bristles that scrapes off black beard algae better than a regular toothbrush can.

YouTube video

How to Prevent Black Beard Algae from Returning

If you have had a black beard algae infestation, the last thing you need is for it to return.

Here are 5 tips:

  1. Ensure that you use a clean up method that will eliminate all of the black beard algae including a strong bristles toothbrush.
  2. Lower the phosphate levels in your aquarium tank. Black beard algae thrive on dead material and waste products that are rich in phosphate.
  3. Increase the CO2 in your tank. This will also help your plant life thrive and produce more oxygen from photosynthesis.
  4. Reduce the amount of time your aquarium is under the lights. Black beard algae thrive in high sunlight conditions so mitigate the amount of time your tank spends under the lights.
  5. Having algae eating fish in your tank is the best way to not only get rid of but keep any future outbreaks of black beard algae under control.


I have now increased CO2 levels and made sure the circulation is flowing better in my tank. I am aware the duration of the lights should be lessened because black beard algae thrives on it.

  • Now that I perform more manual cleaning with a toothbrush that has nice, firm bristles, things are getting better.
  • UV light alone did not work. Red algae or black beard algae that belongs under the category of red algae does not respond well to UV sterilizers and will continue to thrive.
  • Hydrogen peroxide and boiling decorations work too, but make sure your aquatic life is not affected.
  • Overall, my live plants and algae eaters are helping me out more than UV lights to kill black beard algae.

We hope the topics provided help you out to get rid of these problems once and for all.


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Hello, I'm Jason. I'm the guy behind I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.