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3 min read

What do you do if your fish’s fins and tail are looking ragged or discolored? It may be a bacterial disease called fin rot. This illness is simple enough to treat but can lead to other serious complications if left unchecked, so follow our five easy steps for curing fin rot.

How Do I Know If My Fish Has Fin Rot?

Fin rot is commonly found in aquarium fish such as betta fish and goldfish. The symptoms can vary based on how long the fish has been affected:

  • Stage 1: The fins and/or tail start show some discoloration, especially on the edges. Depending on the original color of the fish, the discoloration may appear as white, red, or even black.
  • Stage 2: The fin edges look frayed and uneven as infected pieces start to die and fall off.
  • Stage 3: The entire fin and/or tail has rotted away, and the infection begins to attack the body, potentially leading to loss of life.

You may also notice your fish seems listless or doesn’t feel like eating anymore, since its body is working hard to fight the infection.

Red and white halfmoon male betta fish
If your fish naturally has uneven fin edges, you may have difficulty spotting fin rot.

How Do You Treat Fin Rot in Fish?

  1. Check your fish’s environment
    Whenever your fish gets sick, the first thing you need to do is play detective and find out why the fish got sick. Fin rot may come back again unless you remove the cause of the problem. Check the water parameters with an aquarium water test kit to see if anything is out of whack. Make sure there are no environmental factors causing stress to your fish, like an overly strong filter, sharp decor, or wrong temperature.
  1. Take corrective measures
    After you discover what’s wrong, remove the source of stress immediately so your fish can start recovering.
  1. Clean the fish tank
    Medications often require you to hold back from doing water changes during treatment, so clean the aquarium and remove as much fish waste as possible. (Watch our tutorial on how to properly vacuum your aquarium.)
  1. Treat with medications
    We recommend using a broad-spectrum antibiotic known as erythromycin that is effective against fin rot. If your fish has also developed a secondary fungal infection, methylene blue is an appropriate antifungal treatment.
  1. Make your fish very comfortable
    Keep your fish’s environment very clean and comfortable to ensure a quick recovery process. Medications can sometimes make the water harder to breathe in, so add an air stone or sponge filter to keep the water well-oxygenated.

Green tiger barb
Fin rot can be caused by dirty water, nipping from other fish, or other stress factors.

How Do You Know If Fin Rot Is Cured?

The medication may take several days to beat the infection, but some clear signs of recovery include:

  • The fin rot has not progressed
  • No other new symptoms have appeared
  • Your fish’s appetite and energy level are returning
  • Fin regrowth has begun (and may be a different color than before)

In the meanwhile, you can do several things to prevent fin rot from coming back. Dirty water is a common cause for bacterial infection, so schedule a regular time for cleaning the aquarium and put a weekly reminder in your phone so you won’t forget. Other ways you can keep the water cleaner include not putting too many fish in one aquarium, not overfeeding them, and adding live plants to help absorb some of the fish waste.

As mentioned before, continue to reduce any stress factors in the aquarium by maintaining the proper temperature with a heater, slowing the water current if needed, and removing any aggressive tankmates. Finally, keep a close eye on your fish. It’s easy to miss symptoms if no one’s paying attention to the aquarium, so we recommend examining your fish once a day when you feed them.

Take heart! With proper treatment and prevention, fin rot is an easy sickness to beat, and most healthy fish have no problems making a full recovery. For more information on other helpful medications to keep on hand, check out the following video:

Attributions
Fin Rot on Betta Fish by Dizzy Respect with color adjustment (CC BY-SA 4.0)
Betta Half Moon by Lerdsuwa with cropping (CC BY-SA 3.0)
Green tiger barb by Debivort with color adjustment and cropping (CC BY-SA 3.0)


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