The Best Ways to Remove Brown Algae from the Aquarium.

Brown algae which is also known as diatoms can be very difficult to remove from the aquarium. To make matters worse Brown algae looks terrible and can be harmful to your fish. Brown algae is a unicellular organism that is brown in color it has a bony structure that is primarily composed of silicon nitrate. Brown algae develops in aquariums with high nitrates and sometimes those with high silicon levels. Brown algae can also take over the tank when the lighting is too high or too weak for the aquarium. The best way to remove brown algae is to limit these key factors. Brown algae can be toxic to your aquarium inhabitants and it can also be damaging to the plants (or coral in marine/salt water aquariums) housed in the the tank. Identifying Brown algae is fairly easy usually Brown algae will accumulate over everything including the glass and substrate. Brown algae usually resemble a fine dust ranging from light to deep brown.

Brown algae in a marine aquarium


Listed below are some of the best ways to remove brown algae from the aquarium. Most of these methods aim to cut the nutrient supply for brown algae. Preventing its future growth.

  • One of the best ways to remove brown algae is by physically removing the accumulated brown algae from the aquarium. Use a suction or your hand to remove the algae. The brown algae will spread faster if left in the aquarium and it will be difficult to eradicate.
  • Provide appropriate lighting for not less than eight hours a day. If there are no corals or plants in the aquarium, you can reduce lighting to just 6 hours per day to help in removing the algae.
  • Using filtered water from a RO unit controls the growth of brown algae as this water is free from nitrates and silicates. Check the water from your tap to see if it contains silicates, this is a common cause of brown algae.
  • Nitrate level need to be decreased to control brown algae which can be done by adding a few drops of vodka in the water. Vodka dosing needs to be monitored as it can result in harm to your fish. Nitrates can also be reduced through nitrate absorbing filtrates placed in the filter. Keeping the nitrates low is one of the best ways to remove brown algae and prevent it from showing its ugly head.


  • Cleaning the filters and changing water regularly ensures flow of clean water that is free from silicates and nitrates. Always change the water and clean the aquarium at least twice per week. Clean more if the algae is becoming a problem.
  • Being very careful in marine aquariums to read the label of the salt mix. Be sure to use salt mixtures and rocks that do not have silicate content.
  • Do not offer extra food to the fish. The food that fishes do not consume will just end up as nitrate in the water column. One of the best ways to remove brown algae is by paying close attention at feeding time. Feed slowly for two minutes. Do not let any wasted food sink to the bottom out of sight.  
  • Ensure that the aquarium does not have any loose waste, dying material or it is over stocked. Once again, any of these may increase the likelyhood of nitrates and increase risk of brown algae.

After removing the algae it is imperative to keep a low nitrate environment. This will ensure the brown algae is ‘starved’ and not able to regain growth in the aquarium. If your tap water contains silicates it will be necessary to use RO water during water changes. Brown algae is one of the worst and prevalent types of algae. Getting it under control is difficult but not impossible. The list above outlines just a few ways of containing an outbreak. If you have any added comments or suggestions please feel free to leave them below.

48 thoughts on “The Best Ways to Remove Brown Algae from the Aquarium.”

  1. Episom salt works great also a 1/2 teaspoon per 10 gallon for 1 day a week for 3 weeks works also hydrogen peroxide works but only use in cap fulls per day. Brown algae can also come from drift wood that is not properly clean. Feeding should be on a two day interval add janitors if needed( Cory catfish funnel snails are good they promote airiation to the substrate an they are not plant eaters they only eat algae. Pleco are ok but become aggressive an will eat live bearers an slow moving fish. They do good with algae but slowly eat your live plants. In the wild fish eat once a day an hide the rest of the day. Also lower temp also kills algae …75° an lower 70° higher temp promote growth 76° 89°

      1. Thank you for sharing been having this problem for weeks cleaned it out once only to return days later. Going to try suggestions..

    1. Thank you for sharing. I would like to add that Cory cats are not algae eaters. They assist in the prevention of algae growth by scavenging for uneaten food, which is a source that feeds algae. And pleco’s don’t necessarily become aggressive. They look for an area to clean and sometimes that area is the body of another fish. They don’t discriminate. Unfortunately, Pleco’s get HUGE and are filthy little creatures themselves. Shrimp, snails, Siamese algae eaters, and Otocinclus are the preferred choice for removing algae via fish. But make sure any fish you get is compatible with current stock.

    2. Turn lights off! There is conflicting info on the internet about more or less light. I’m telling you – turn off the lights! Algae is a plant, therefore it needs light for photosynthesis.

      1. By the way, Brown algae a nickname because it is similar in appearance. In reality it is not a plant. Its a colony of diatoms. Actually a single celled creature.

    3. I have a small 1 or 2 gallon fish tank…not sure. With 1 betta fish – what or how much epsom salt could I add to the water to get rid of the brown algae?

    4. Thank you for the information. I have a 60gal tank. What is the amount of hydrogen peroxide to use?
      Thanks again.
      Angie W

    5. Hi, do you add the Epsom salt with the fish in the tank? Apologies for being such a newbie in advance and asking stupid questions. 😀

  2. I think a big one as well depending on the size of the tank is taking the time to try and brush off some off the algae on your plants. It’s tedious but if you are having growing issues and your plants are covered in the stuff then their growth will be reduced

  3. I can not control this ugly brown algae. It grows in the center of my 40 gallon freshwater tank. I have physically removed it by extracting the gravel (several times) and it keeps coming back. Last water change, I used a special filter and it is back. I’m going crazy with this.

    1. Sounds like me, a year ago. My problem has greatly decreased by buying a Green Machine UV sterilizer for about 40 bucks. It does plug sometimes, but I bought a plastic turkey baster and cut the end off to match the diameter of the intake, for flushing.

  4. I tried no light for 48 hours ….. the brown stuff took off like a bat out of hell .. so sorry but reducing light doesn’t work.
    I have top of the range plant LED light on my tank for 9 hours a day … also doesn’t get rid of brown stuff (not an algae so I’m told)
    I suspect our tank water may be high in silicates (I water change 10-20% twice a week and vacuum up any waste), but don’t know how to test for this – can anyone help on that one?
    Glad to hear that vodka might work as well on the brown stuff as it does on my bad back (internally LOL), but how much for my 100 gallon?

  5. I had this problem
    I tried manually cleaning the aquarium…stones..the decorative items etc repeatedly
    Nothing worked
    I added two small tank cleaner fishes
    In imy aquarium i have only gold fishes
    The tank cleaners cleared up the brown algae (diatoms) within 24 hours
    No more of this prob

  6. Thanks for all the great info. I have a 20 gallon aquarium that now has 1 med size (2″) fantail goldfish. My small pleco died. I am struggling with brown algae. I purchased a product from Walmart that specifically says it will get rid of the algae, but that I also must clean as much of it as possible & as the algae dies clean & or change the filter as well. I would love to have something alive to clean the algae instead of using chemicals so what are some of the best kinds? I believe someone mentioned a mystery snail to me once, but snails make me nervous because I have had them completely infiltrate my entire tank & filter system before so haven’t had any for years. I live in Kansas City & I believe our water is basically toxic. I drink at least 90% bottled & filtered water myself. Thank you for any additional advice

  7. So yoU have an axalotl in my tank that I’ve had for 1+ years now and this stuff showed up. If I put any other living creatures in the tank with her they end up eaten. My tank also maintains a temp of 64-66F. Salt will also harm her. I’m afraid I will have to scrap this tank and start over. Any ideas to help?

  8. i had same problem so done 20% water changes weakly plus i added 2 sponge filters to my fluval 57 and washed my decor in hot water before putting back in tank plus netted the algae once a day also rember to gently clean plant leaves with finger tips this will help andafter a couple of weeks tank should be clear

  9. This all started because my teenage daughter brought home a goldfish bowl with 8 fish in it. Obviously, she was clueless about what was required to maintain an environment where fish can survive. I was a veteran of aquariums, but on a larger scale. I accepted the challenge of rescuing the two remaining fish and showing her how to provide an adequate environment for fish. I ended up trying to maintain a 6.7 gallon aquarium all on my own without her help and had to deal with a myriad of re-occurring problems. It was just one thing after another. As soon as I would resolve one problem, another would manifest. It may be related to the size of the tank, since in a small area, problems are magnified exponentially. I did overcome many problems with this aquarium and just when I thought I had all problems resolved, this latest appeared in the form of this disgusting brown slime algae over the course of just several recent weeks. Where did it come from?? It was never there before, but I did make a change to the brand of flake food I was feeding my fish. Is this the culprit? I now have to do extreme water changes every 10 days and it comes right back with a vengeance. I am willing to commit at this point to an algicide to eradicate this pestilence once and for all. It’s not good for the fish, but it seems the only other option is to start completely over. Any thoughts?

  10. P.S. to my earlier post – someone said that a Green Killing Machine would take care of the problem. However, I tried that and it didn’t seem to work on this brown algae. It worked great on a bio-bloom and a green algae bloom, but not on this species. Maybe the UV bulb is weak and needs to be replaced.

  11. Ok, so can I add the epsom salt into the tank without cleaning out any of the brown algae? Or, should I give my fish a temporary home, clean the tank, refill the water, then treats the water ?

  12. Why are there no answers to all the questions here? I have Epsom salt and peroxide.. How much to use? I been asked lots by others.. Somebody answer our questions? I have a 30 gal tank.

  13. I can see lots of ppl with same problem , few tips , but then no one replied about peroxide or Epsom salt, even vodka lol

  14. Awesome stuff! I have a 20 gallon with a persistent brown ‘algae’ bloom, all over one specific plant and the lava rock.

    I’m going to actually try clearing all waste in the tank, brushing down the brown “algae,” do a 1/3 water change, and cutting the lights for a day or two. Keeping an eye on everything all the while, brushing down remaining spots, and I’ll start again with 8 hours light. We have well water that’s always tested well (no pun int’d) for aquariums, but I’m starting to suspect I may simply have my tank overstocked with too many plants and 5 thriving snails, and haven’t been doing water changes as frequently as I should. I have new filters on the way for my Biowheel 150, and I’ll be putting in two(!) new filters to buff up filtration. I’m even considering putting together a second, smaller tank and splitting up the snails and plants between the two. So it begins….

    Other than the so-called algae, everyone’s doing great! Thanks for the suggestions. I’m sure more frequent changes to keep up with the nitrates/waste will help the problem.

  15. OK, “silica” is misleading… the issue is “Hard Water”. Do you have Hard Water? Simple way to know, does your shower head clog up with crust? Does your toilet bowl get that crusty ring at the water line? Yep, you guessed it, you have hard water. You could spend money for a TDS (Total Dissolved Solids) tester, but really, hard water should be fairly obvious.

    Reverse Osmosis filter removes 99% of TDS in water. They can be pricy, but are worth the investment, especially if you have a large aquarium. The grocery store water vending machines dispense RO water at a reasonable price. Great option for small aquariums.

    Hope this helps

  16. Epsom salt: Use 1 tsp per 10 gallons of water. Peroxide: Use 4 drops per 10 gallons of water. (Side Note: Peroxide can also be used as an emergency oxygen booster in the event of a long term power outage.)

  17. Hi all… I’ve been looking for a way to get rid of the brown algae in my tank as I’ve recently acquired one here in the UK and I’m still getting used to the water parameters as they are quite different to what I was used to in South Africa.

    We had a few fish tanks, but please bear in mind that we are no experts and I’m just giving you personal experience from what we learned and went through.

    We had brown algae as well as green algae, the best thing we used was water from the tap that we treated with Seachem Prime and Stability (we left this in a barrel overnight) in order to perform our water changes. We would only change about maximum 30% at a time. At the same time, using a siphon to thoroughly clean through the substrate, removing our ornaments and cleaning them gently and removing all traces of algae in a bucket with 1 part water and 1 part distilled white vinegar (we researched this and found it to be the best to clean our new tanks, etc.)

    We also decreased lighting and that seemed to helped but only with the green algae. I hope this helps someone 🙂

  18. Appreciate all the feedback & comments, great stuff to consider in the quest to eradicate brown algae.

    Our solo fish, Bob the dancing betta, recently graduated from a 3 gallon to 8 gallon tank. We have 2 fabulous & active snails Gary & Harry, and a healthy plecko, Perry. Since upgrading the square footage, it seems the cleaning creatures can’t keep up or make an impact on brown algae.

    I’m intrigued by the Vodka suggestion and will be trying the salt & possibly hydro-peroxide. I think overfeeding is a factor too for a solo fish, so we’ll cut back on frequency & amount of food.

    Thanks again for all the feedback, very informative & helpful!

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