How to get rid of black algae in an aquarium

January 4, 2016

For years, well really nearly 3 decades, my father and I have been raising tropical freshwater fish. Occasionally the tank will somehow acquire a growth of black algae.

Black algae is insidious. Once you get it it is impossible to get rid of without tearing the tank apart and bleaching everything. The danger here is that bleach is highly toxic to fish. Even a single drop can kill off an entire 120 gallon tank full of fish.

Maybe the most popularly debated topic online is how to get rid of black algae, and until now nothing has worked.

I accidentally ran across the answer over a month ago!!! Here it is:

My heater (~16 years old!) failed and failed on. The temperature in the tank spiked to 110F before I noticed.

Over the weeks the tank, which previously was completely covered with black algae, has cleared up. Even the normal green algae is gone!

I do not recommend getting your tank that hot with the fish in it. All but 2 of my fish died :(. You can put them in a temporary holding tank, or buckets, while you heat up the tank.

I am curious to know of anyone else out there who has tried this method and how it worked for you.

Edit (Feb 2017): Noting from a commenter- My tank did not have any live plants in it. They are all plastic.

Here are a couple pics of my tank today. I wish I had a before pic to show you, even the plants were covered in the black algae.

IMG_2518 IMG_2519


58 thoughts on “How to get rid of black algae in an aquarium

  1. Oli (June 26, 2016)

    I’ve been using a siamese algae eater with huge success. Within a week the blackbeard algae was knocked down to a fine fuzz, even after removing the Siamiese Algae Eater to another tank, the algae has not returned.

    1. Ben Lobaugh (blobaugh) (June 29, 2016)

      Excellent! I thought that I had tried a siamese algae eater previously but I will definitely try again next time!

      1. Julie Goodwin (June 22, 2019)

        Hi I don’t have black algae,I just want to say Thank you for sharing your unfortunate ordeal, and coming out of it with a solution for getting rid of black algae. That deserves at least an atta boy. I’ve learned something by clicking on your site and that’s a good thing. Thanks

        1. Linda Ware (December 10, 2019)

          Me too!! Thanks and Merry Christmas…

  2. Vickie McBride (September 9, 2016)

    Thank yu I am going to Pet Smart today for a Siamese Alge eater!!!!

  3. Wayne (September 29, 2016)

    Very interesting……high heat! How long was the tank at 110F before the black algae died and or disappeared? Also, a Siamese Algae eater? I’ll have to get one too; but I’m very interested on the high temperature in the tank. I’ve gotten black algae on the rocks, too…..a real pain! Thanks for the tips and how long on the high temp?

    1. Ben Lobaugh (blobaugh) (October 18, 2016)

      I think it was less than an hour. The longer you can go the better. Just make sure you get your fish out of there first!

    2. Mike Kutz (December 5, 2017)

      I imagine it will kill any living plant? I have a live plant tank with a black algae problem. I had to close down 1 tank because of it and I STILL can’t get that crap off the glass… even after soaking it in a water and vinegar solution…

      I guess what I’m asking is off it will kill all my plants as well??

      1. Ben Lobaugh (blobaugh) (December 6, 2017)

        Hi Mike- My plants were plastic so I cannot give you a 100% sure answer. I would guess that live plants would be damaged however.

  4. Bob Carney (December 7, 2016)

    I have a 75 gallon tank that has become full of the black hairy algae, even my live plants. I reduced my light from 11 hours to 10. What do you suggest?ben.

  5. Yoshi (February 9, 2017)

    Wow! This is really interesting!

    A question though. Did any of the plants die from the heat?

    1. Ben Lobaugh (blobaugh) (February 9, 2017)

      The algae did! I have no live plants in my tank. I would imagine they would have issues though since the algae did.

  6. Yoshi (February 16, 2017)

    I tried your method. In a bathtub though. My problems were BBA on the actual plants. All plants survived except for moss balls. The round japanese thingys. Got rid of all BBA. Thanks for the suggestion and maybe you should’ve said in your post that you had no plants.
    What I don’t get is why you didn’t take out your fish and cleaned your tank manually since it can be washed away if you scrub it off with a scotch bright sponge.

    1. Ben Lobaugh (blobaugh) (February 16, 2017)

      Black algae is insidious. The only way I have been able to get rid of it “manually” is to pull everything out of the tank (fish, plants, rocks, decor, etc) and bleach it all (except the fish of course!). There are a couple issue with this method, the first being that bleach, even a tiny amount, is highly toxic to fish. It takes a lot of work to get the bleach out completely. And second the container with the fish has water in it that contains the black algae spores. When you put the fish back into the tank by default some of the spores will come in with them.

      Plus, this method I ran across entirely by accident when my heater broke 🙂

      1. Ben Lobaugh (blobaugh) (February 16, 2017)

        Though keep in mind you do want to take the fish out of your tank before using the heat method! That means you will run into the similar issue of spores in their container.

    2. Sarah (May 30, 2019)

      Yoshi. We have been scrapping black algea off our walls for a month now. We lost our algea eater to the black algea eater…

  7. Yoshi (February 17, 2017)

    Thanks, no I understood all that. Thing is, I found your post just Googling for help against BBA. It was a pleasant surprise that something as simple as overheating could kill of this #€%&=!°”%%! I understand that you don’t want to bleach your tank. In my case, I can’t. Many things are built in in the background and are made of styrofoam.
    But I took my roots and my plants to the bathtub which I had filled with 45°C water. Sank them for like 1,5h and then placed them back into the tank. No fish were harmed or included in this procedure. Got rid of EVERY BBA there was except for the ones that exist on my backdrop. Can’t move that one, it is glued where it is. Anyway, removing 95% of all BBA is so much better than how it was. Plants were dying and I think I can see a co-relation between bloat and BBA. No more bloated fish at the moment. Had a death per day before this procedure.
    Problem though is that all my Marimo moss balls turned greyish and the majority of their outer build/surface/depth got ruined. But my Sailfin Gibbiceps have now eaten through all the decaying layers and right there, below all this grey is actually green. It’s like 1/4 of the original plant that is still green. I have hope.

    There are a few methods, like Flourish Excel to wipe BBA out entirely but I can’t do that to my fish and aquarium since my PH is on the edge of being to low and I can’t take the risk of going below that.

    All I said was that your blogpost never mentioned that you didn’t have any plants to start with. I thought reading it, that you saved plants. The other stuff like glass and all can be scrubbed off with a scotch bright sponge

    1. Ben Lobaugh (blobaugh) (February 17, 2017)

      Awesome that it worked out well for you too. Thanks for describing the method. I too was having strange health issues with the fish before this happened. Had a couple clown loaches starve themselves to death and other fish mysterious floating every few days.

  8. Gregg (March 12, 2017)

    Hi Ben, very interesting post. I too have black algae on my plastic plants and decorations and it is absolutely driving me insane, to say the least. I’ve taken them out and scrubbed only for the Algae to return within a few days. You mentioned taking the fish out and raising the temp in the tank to 110 degrees but you did not state where you kept the fish and for how long you kept the temp that high before returning the fish to the tank. A bit more insight would be really helpful to me and any suggestions would be greatly appreciated.

    1. Ben Lobaugh (blobaugh) (March 13, 2017)

      Gregg that is because I did not take my fish out. Unfortunately the heater went berserk and most of my fish wound up dying from overheating. I think 3 of them survived. I am not sure exactly when it happened, but for the water to get that hot I am guessing it was more than a half hour.

  9. Sharon (July 23, 2017)

    I have a big piece of wood decoration in the tank. how do I clean that ?My heater is iffy working, and i dont know where i would put my fish anyway. Suggestions or comments would be helpful. Im bleaching the plastic plants already, I thought that was the thing to do. Hope that is ok??

    1. Ben Lobaugh (blobaugh) (July 24, 2017)

      Yep, bleaching plastic plants works just fine. I did it as well. Be sure you get all the bleach rinsed off. Even a drop can kill an entire tank. For the wood try taking it completely out of the tank and putting it in a bucket or bathtub. If it is real wood be careful about bleaching it. My father bleached a piece of wood and spent a week rinsing and drying it and some small crack still had bleach and killed off a 130 gallon tank :(. I would try the heat method with it first.

      1. Sarah (May 30, 2019)

        Hey so i have a 400 gallon tank. Will this break my glass heaters? I can remove the fish temporarily no problem. Just wondering…is it all of the tank?

    2. Genel (June 7, 2019)

      You don’t need to bleach you plastic plants. Just set them out in the sunshine and the algea will be gone the next day. Becoming dry in the sunshine, with the warmth and the bright light gets rid of it completely.

      1. Ben Lobaugh (blobaugh) (June 7, 2019)

        This is neat! The sun kills black algae? It seems that even after drying in a tank that has been sitting for a while it comes back to life. If sunshine ills it dead that brings up some great possibilities.

  10. Rob (July 28, 2017)

    Thanks a lot mate very helpful post, I just wish some other readers actually used some common sense instead of saying you haven’t provided enough info. I’m go to transfer my fish into a breeding tank and turn the heat up on the BBA. I will let you know how it turns out.. Regards Rob

    1. Liza (August 9, 2017)

      How did it turn out?

  11. Desiree Anne Alexis de Souza (August 12, 2017)

    Thanks for that really helpful info. I have been trying to get rid of the BBA but its just seems to keep coming back. Even removed the infected live plants but didn’t work. Will try the heat method and report back.

  12. T (August 13, 2017)

    Great post thank you I’ll try this method

  13. Larry (August 20, 2017)

    I have a 20 gallon tank with just a couple of small black moors and one small fantail goldfish in it. I too have noticed some black algae growing on my plastic plants and now the small fantail has all of its fins starting to show black markings showing on its fins, fan tail, and gill covers. Can this stuff grow on the fish itself? Can’t tell if the black moors have any growing on them for obvious reasons. Is this stuff fatal to the fish?

    1. Ben Lobaugh (blobaugh) (August 21, 2017)

      Hi Larry,
      I am not sure that that is algae. I have never heard of algae growing on fish. I am more inclined to thing it is some sort of fungus. Check the water quality and check the fish for injuries. Most good pet/fish stores can do great water tests if you take them a sample.

  14. Justin (September 1, 2017)

    I have had a battle with BBA for around 5 years in my tank it just keeps coming back.
    The heat treatment sounds like a good option, although I am completely rebuilding the aquarium due to being fed up with the algae.
    If it returns I think that will be the end of my fish tank.

    1. Linda Ware (December 10, 2019)

      I agree. I have a 55 gallon that I’m trying to sell for 100 bucks, stand, and hundreds of dollars worth of supplies. I can’t take it anymore

  15. Frank (September 16, 2017)

    Hi Ben I love to try your method and I understand your fish tank water temp get to 110 from the heater that went berserk but what about the heater that function normally my heater only can get up to 86 degree. So how to I get the water hotter than 86? With hot water? May be??

    1. Ben Lobaugh (blobaugh) (September 25, 2017)

      Hi Frank! Yes you could pour hot water into the tank. Be careful with that method. If you pour it directly on the glass it can heat up too quickly, expand, and crack.

  16. Larry (September 17, 2017)

    Hi, Ben! Just an update on black algae in one of my 20-gallon tanks. This is the tank with one fantail goldfish and 2 black moors, altogether about 5 inches of small fish. I had a lot of black algae in this tank, including black algae on all of the fins, gill covers, and mouth of the goldfish. Per lots of your suggestions, I siphoned all of the sand in the tank, took out the plastic plants and soaked them in hot water (at least 115 degrees) several times over a couple of days. Finally, I started paying more attention to the amount of fluorescent lighting per day and really cut back to feeding lightly twice a day. I also began a regimen of changing about 1/3 of the water twice a week. Miracle of miracles, the black algae disappeared (about 95 % at this point) from the goldfish with just a smidgeon on the tail fin. After rubbing off what “old” black algae remaining on the plants, I replanted the tank. So far, no more appearance of black algae in the tank or on plants. Thank you for your suggestions. Oh, by the way, the tank has always been unheated.


  17. oldchopper (September 20, 2017)

    be careful when u buy fish and plants for your tank usually a cause for sudden black algae groth is something introduced into the tank that has the algae on it, it only takes a few particles to kick things off and u have a nightmare to deal with. I found many years ago that the best way to deal with it was throw all your plants away, remove all rocks and gravel and treat it with boiling water, scrub your tank with fresh water and hard work then pour boiling water all over the inside a few times to cook any remaining particles (be careful with boiling water on glass do this step slowly, to much heat to fast may crack the glass). Anything treated with boiling water will be cooked and will not grow any more, any algae on the rocks should have turned red and u might find some of your fish will actually feed on it. personally i would never use chemicals to treat a fish tank i think that is a disaster waiting to happen worse than the algae. Also be careful where u shop i have seen a lot of pet shops selling fish that seem to think black algae is acceptable, these people surly have no idea how to maintain an aquarium and do not care.

  18. Sak (September 21, 2017)


    I have met the dreaded BBA monster on numerous occasion and I can tell you there is nothing more annoying. I have tried the heating approach or the ‘rage’ tearing down tank approach. All worked with mixed results. Until 2 years ago, I came a product called aqua evolution bomb. I used it in combination with DD rowaphos. Put both of them in the filter (make sure the filter turns over the tank at least 5 times in an hour) after a couple of weeks, mr BBA seems to take a very long leave of absence

  19. Tabi (October 7, 2017)

    My tank suffers from black algae. I have driftwood, rocks and plastic plants, along with gravel. I take everything out of my tank weekly and soak in bleach water. Then I change 25% of the water and scrape the glass. I have 4 Japanese Coi that are 11 yrs old in my 55 gallon. I do this weekly!! And still, suffer the dreaded black algae. So the manual thing is a temporary fix. I believe it lies within the gravel, so I will be trying the heat method with fingers crossed.

    1. Ben Lobaugh (blobaugh) (October 31, 2017)

      Hi Tabi- You are solving for the symptoms not the root problem. The algae spores will be living in the gravel and in the water in the tank itself. That is why it is so insidious to get rid of!

  20. deborah (October 30, 2017)

    how long did you heat the tank up for?

    1. Ben Lobaugh (blobaugh) (October 31, 2017)

      I am not sure how long the tank was hot. It happened as an accident. Long enough that it killed all but a couple of the fish 🙁

      1. Eliot (November 2, 2017)

        Are there any black algae recurrence after the heating incident?

        1. Ben Lobaugh (blobaugh) (November 2, 2017)

          Nope! It has not come back, but then again nothing new was introduced. Black algae can definitely reoccur if the spores are introduced again. This is pretty common to find in water from fish stores.

  21. Eliot (November 3, 2017)

    Good to know! 🙂 I’ll probably give it a go if Flourish Excel way doesn’t work out, costly but lower risk. BA was introduced into my tank from a mistake of mine to another. Panicked when I caught my ghost shrimps feeding on the newly bought anubias petite in my quarantine tank made me immediately transfer the anubias into my fish tank. It was then I noticed there’s a small fluffy algae on the wood the anubias is on, kinda expected it will come back to haunt me even after I removed it, alas.

    Its under control for a year now with water change & help from a hardworking SAE. (PS : Try to get juveniles instead of adults, I could be wrong but, feel like it learned to pickup the habit of eating the type of algae in your tank as it grows) Tho I do wish to get rid of the BA once and for all and this heating method might just be the giant RESET button I’m looking for 🙂

    Its a lowtech planted tank, fingers crossed some will make it through the boiling phase tho I can almost guarantee the carpet plants won’t make it & killing the nitrogen cycle. For science I’ll probably test it on my 5g quarantine tank first by gradually adding in hot water every minute, slowly raising the temperature while monitoring the temperature to avoid glass cracking. When you mentioned “more than half an hour”, did you included the time for the water to cool down after you turn the heater off?

    1. Ben Lobaugh (blobaugh) (November 3, 2017)

      Because my fish were in the tank I pulled out buckets of hot water and dumped in cold water. Remember it was by accident this happened. If your tank has live plants I definitely think you should test first. I am not sure how they will respond to the hot water.

    2. Stephanie (September 6, 2021)

      I’m gonna do this with along with another method I read about. I’m going to gravel vacuum, then I’ll pull my pants and other live stock out and I’m going to use a spray bottle with hydrogen peroxide/water mix and spray decor and gravel. I’ll dip the plants in a peroxide dip too. Hoping for the best!

  22. Marcie (December 1, 2017)

    I am currently starting my second round of trying to get rid of the black algae. The first time I didn’t change out the gravel so this time it’s all going. My question is that when I bleached the large rocks, the algae “hair” was still there but it was hard to see because it was now white or clear. Do you know I can actually remove it once I have bleached it?

    1. Ben Lobaugh (blobaugh) (December 2, 2017)

      Hi Marcie- The only way to remove the physical presence I know of is to scrub it. What I have done to clean dirty gravel in the past is to fill a 5 gallon bucket with gravel and put it under the faucet in the tub. I then will sit on the side of the tub with warm water running into the bucket and agitate the gravel with my hands until all the water coming out of the bucket is clear. I do not know if that will work on the dead algae but it may be worth giving a try. My guess is the gravel rubbing together will scrape the dead algae off. If you do it I would love for you to report back here with the results!

  23. Oven (January 9, 2018)


    I just discovered your post after witnessing the same effect of temperature. My live plants were all covered in black, then my fish got ich parasite. Treatment for ich is to raise temperature to 30 degrees Celsius for two weeks, I used to have 25. And I also put a lower dose of recommended salt NOT to harm plants and some sensitive fish. One week later the ich is gone, but there was a great side effect of treatment, the black algae was just peeling away from the leaves! So I guess you don’t have to use excessive temp, even safe temperature for fish and plants but on the high end would gradually help eliminate black algae.

    1. Ben Lobaugh (blobaugh) (January 9, 2018)

      Hey that is cool to know! Thank you for providing an update.

  24. Shawna prophet (January 9, 2018)

    This is driving me crazy have a 50 gallon tank have emptied it out twice still grows on the side of my tank I am completely worn out with it I guess I should just throw away this tank and start over with a new one please help

  25. Biggmatt (February 19, 2018)

    Shawna I had the same problem try emptying the entire tank scrubbing clean then heat the tank with a hairdryer then repeat once more make sure to do this to all decorations except living plants and fish also transfer fish with a net so you can take the least amount of water witch will be carrying spores.

  26. Grudge (February 21, 2018)

    I have a discus tank at 29 degree. Balls of black algae over everything . Wood, plants floor of bare tank. 450l tank

    I’ll try the heat approach and bleach. Looks like I’ll be starting again it’s really frustrating. My question is, what about the filter I’m guessing we keep it running ??

    1. Ben Lobaugh (blobaugh) (February 22, 2018)

      What kind of filter do you use? I am strictly under gravel so it does not matter. If you are putting bleach through any other type of filter that has a filtration element you better make very very sure all of the bleach is out. Discus are sensitive under regular circumstances, even a tiny amount of bleach is not going to make them happy.

  27. Lukasz Polanski (February 28, 2018)

    Hi. I have had a problem with the black algae and was getting desperate. I have a 70L (apologies for the units) tropical tank. I was on the verge of getting rid of everything and starting anew, but decided to try a few things first. I have increased the temp to 30 degrees C, increased the amount of light to 8 hrs a day with an increase of liquid carbon (double the recommended dose) and bought 2 Siamese Algae eaters! As if by magic- within a week no sign of the black or any other algae. The algae eaters have been amazing and are keeping things in check- plants seem to be much happier as well. My tip- get the algae eaters and improve the environment for the plants- works so far, and didn’t have to start from scratch!

  28. Kim (May 25, 2019)

    Hi, I know im a little late to this thread but I was having a black algae problem and did a search that brought me here- and I’m so pleased that it did! You guys reminded me of my late dad- when we were little he had a huge tank and he at some point had this very problem, he solved it by stripping down the tank (I know it’s a pain🙄 but bare with me) he NEVER ever used bleach. He boiled his gravel, scrubbed all natural rocks, wood etc then baked them! Not live plants obviously, any seriously effected he would scrap but they all got a good thorough rinse and a wipe down
    if possible beforee going back in the tank, it worked wonders! He had that tank from before I was born right up until he passed (I was 17 then) and he only ever did it twice. Thanks to you guys for fond memories and a solution 😊👍

  29. Edmund Menifee (August 1, 2020)

    Awesome 🙂

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