How to Cure Fin or Tail Rot on Your Pet Fish with Peroxide

Traci Brown
Aquarium owners know that some illnesses in fish aquariums just won't go away, regardless of what they try. However, there seems to be more than one way to solve some fish illnesses and sometimes those involve using regular household products. Fin and tail rot can be cured, and quite easily by using regular peroxide.

First, you'll need to prepare for this process, which some fish owners call 'surgery' but is far from that. Set aside a cup of treated tap water. This cup of water will be used to rinse your fish later. Take your fish and place him in a smaller container, one of which that can be easily transported to and from the closest sink. Have another container on hand with treated, room temperature water so you can place your fish into the new, clean water. You will also need a fish net, some paper towels (one paper plate and a paper towel can be used, depending on your preference), a bottle of peroxide, and some q-tips.

Lay out a clean paper towel (or paper plate, whichever you are using) and fold another paper towel over and over to make it small enough to cover the head of your fish. Dip this paper towel in clean, treated water and set it aside. Take your fish from his cup and place him on the paper plate. Quickly cover his head with the wet paper towel and hold the two ends. This will help calm him, and keep him from flopping if he gets frustrated.

Next, you'll dip one end of a q-tip in the peroxide and begin to paint your fish. Very gently slide the q-tip over his fins, making sure to get any blackened edges, or area's of the fin that the rot seems to occur on most. The fin may 'fizz' or bubble a bit, but this is common, especially if their fins are being attacked by a lot of bacteria or fungus. You may also notice a bit of blood or a blackish looking substance on the end of the q-tip. This is completely normal.

You'll want to leave the peroxide sit on their fins for a few seconds. Make sure that you only paint the fins and nothing else. Do not get the peroxide near his gills because this can cause complications, even death. After the peroxide has set for a few moments, remove the paper towel and dump the fish into the net. Take the treated water that was set aside earlier and dump it over the fish. Continue until the entire cup is empty. Shake him off and put him into the other container you had set aside earlier.

Your fish may act very angry after this process. He may quickly swim around, or shake out his fins as if he was trying to remove something unseen. For the next 24 hours, his fins may seem dull and colorless; they may even look 'melted'. Don't worry, this is normal. Some fish may act a bit shocked, and sit at the bottom of the tank without swimming much. You can make them comfortable by covering their tank in a towel and checking on them every so often. The towel minimizes outside stressors. Products such as Melafix or items that help replace their slime coating are excellent items to add to a tank after a painting. This helps replace the slime coating which ensures that electrolytes are not lost, which can be harmful. Aquarium salt can also be used which also helps replace electrolytes and it helps reduce fish stress. Add no more than the recommended dosage.

And remember, this should only be performed if you are comfortable with the process and after all other treatment methods have failed. Perform this treatment at your own risk.

Published by Traci Brown

Traci has a Bachelors of Science degree in Child Development and Family Studies. She is currently working as a Preschool teacher, an English tutor and as a writer online.  View profile

  • This should only be performed if you are comfortable.
  • All items should be laid out before beginning.
  • Any water used during the painting should be treated and left to age for several minutes.

7 Comments

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  • Jen11/23/2010

    I can't thank you enuf for the suggestion to use peroxide. It saved my fish:)

  • Stuart Halliday1/28/2010

    But this doesn't treat the underlying reason why the fish got infected in the first place.

    Treat the tank weekly with a 'competitive exclusion' waste control bacteria bottle and you'll drastically reduce the levels of bad bacteria like Aeromonas, Pseudomonas, Flexibacter, etc.

    Don't live in the dark ages...

  • marie1/4/2010

    i have a crown betta overnight his top fin and around his bottom tail lookked liked they bitted off what could have happened and no other fish has ever gone near him

  • Traci Brown9/25/2008

    A cottony looking growth on the fishes tail sounds like a fungus infection. Clean the fishes tank and put in nice, clean water. If you have any aquarium salt, add a bit to the water and find a medication that treats fungul infections, including fin and tail rot. If after a few doses that does not seem to be doing the trick you may have to try painting the fishes fins with the peroxide. Don't forget to keep the tank temperature at the temperature recommended for your fish to thrive.

  • Adma9/25/2008

    My dauters fishes tail is rotting away what sould i do?You can see like a kind of white stuff what is it?

  • B Rayner3/3/2008

    Have small cotton wool type growth on the tail fin any help on a cure would be appretiated

  • J. E. Davidson4/1/2007

    Soounds like it would work. We are getting ready to buy some fish for the aquarium we have set up. I'll have to remember this tip if we have rot problems.

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