• Archives

  • Categories

  • Pages

  • Follow me on Twitter

How do I treat Fin Rot or Tail Rot? – Water Garden Q & A

Picture of Tail Rot

Q: My mother-in-law has a water garden in her yard. One of her gold fish now has no rear fin. It looks like he had gotten stuck between some rocks or something had gotten a hold of it. The fish is now laying in the rocks, but having a hard time swimming. What do I do? -Faith of Granite Falls, NC

A: When a fish begins to lose their fins or tail, it is usually referred to as “fin rot” which is a bacterial infection. This can happen for many reasons such as stress, poor water quality and/or an over population of fish. Any one of these can all cause a fish’s immune system to become weak making it vulnerable to bacterial infections.

If your fish already shows signs of “fin rot”, the following is recommended: Melafix , Pond Salt and Medicated Fish Food. This will treat both externally and internally. Depending on the size of your pond and your ability to isolate sick fish you can choose to treat your entire pond or set up a treatment tank.

Good Fish Keeping Tips to Prevent Diseases:

1.) Use Pond Salt to lower stress. Adding pond salt to your pond will lower stress as well as treat for almost 80% of the common fish diseases.

2.) Maintain good water quality! This can be accomplished by having an adequate filtration system, reducing fish population, less frequent feedings (and use high quality fish food) and by adding natural bacteria such as the DefensePAC® to reduce excess nutrients.

3.) DO A SPRING CLEAN OUT!!! Empty the water out if possible, power wash and remove bottom sludge and algae. Oxy-Lift™ Defense® can be a great tool when doing a clean out or performing regular maintenance.

4.) Perform regular water changes. You should do a 10-25% water change every 1-2 weeks. When doing water changes it is always recommended to use Water Conditioner to remove and detoxify chloramines and heavy metals.

5.) Add floating plants such as Water Lettuce and Water Hyacinth to reduce excess nutrients.

Melafix Dosage rate:
You will need ¼ cupful (60 ml) for every 600 U.S. gallons (2,280 L) of pond water. Repeat dose daily for seven days. Results can be seen is as little as four days.

Dosage rate for Pond Salt when treating for disease:
Use 5 cups of salt per 100 gallons – Note at this rate you will have to remove pond plants from the treated pond. If removing plant is not possible, isolate the sick fish into another tank with vigorous aeration.

Dosage rate for Pond Salt to prevent diseases:
1-1/4 cups per 100 gallons (for ponds with plants) and 2-1/2 cups per 100 gallons for ponds without plants.

14 Responses

  1. Great article. I was not aware that you can use the salt in a pond as well (only know from fish tanks). In fish tanks you usually change water to get rid of the salt. How are you doing it in a pond? Thanks.

    Kind regards


    • Andy – You can perform partial water changes in a small pond as well. This also helps reduce suspended organics while adding fresh, oxygen rich water.

  2. Help me my fish is dying of fin rot what do I do this is the second goldfish I had that is dying of fin rot the goldfish fish now Mercedes is stuck to the filter and when I get her off she just floats around until she gets stuck again that is how my other goldfish acted I tried everything please help me

    • Hi Kels – I would treat with an antibacterial medication such as Wipeout. Right now your fish are getting into the filter because they are weaker. Get the fish into a smaller tank with clean water that is well aerated. The small tank will be easier to treat and keep the fish contained. Good Luck and I hope your fish pull through.

  3. pond size 50 deci mile. depth 5ft. koi quantity 10milion,size 1inch, after longtime high tempareture yestarday sudden fall of temp.occurred, koi become week and boiled like.after rain fall, please
    give your treatme

    • Hello – It sounds like the fish may just be stressed from a quick change in temperature. Do you have an aeration system for the pond? That would help keep water temperatures more stable and increase the oxygen content in the pond to reduce fish stress.

  4. Janice,

    I would agree that you are beginning to have too many fish in a small 110 gallon pond. You will be okay as long as your filter is capable of handling that kind of fish load. Overcrowding a pond with fish can cause fish stress which can lead to the fish becoming more susceptible to disease. So please keep that in mind.

    As for adding the fish that may have a possibility of having fin and tail rot, I would not recommend it. I would keep it isolated and keep treat it as you are before adding it.

    Keep an eye on it to see if the discoloration on the fin/tail gets worse. The discoloration is usually the first sign of fin/tail rot.

  5. Actually I need to add that the sick looking on is “calico” and I’m not positive it’s fin/tail rot – it might just be that his fins and tail are supposed to be funky looking… The actual tissue seems well shaped just colored like fin/tail rot would be in a normal goldfish.

  6. I have a 110 gallon outside pond with 5 large (7 year old 6-8 inch) fish. All seems well but the kids won 5 small fish at the fair and one of those has fin/tail rot. Is it safe to add them all to the pond (I actually put the first batch of healthy ones (3) in the pond, the other 2 are in isolation)? Is this too many goldfish for 110 gallons? I have treated the sick guy with melaluca 1x day for 7 days and done some water changes.

  7. The major cause of fin rot is the poor water conditions. If the water conditions continue to be poor, then the fish’s stress level can increase and this wears on the fish’s immune system making them more susceptible to getting fish rot or other diseases.

    Think of it being outside is bad weather conditions, the same thing will happen to your body causing you to be more susceptible to sickness.

    Hopefully this helps.

  8. Is fin rot a contagious disease among fish? I only have one shumbin with fin rot and my pond is not overcrowded.

  9. Great article on ” How To Treat Fin and Tail Rot On Goldfish “!

    The good news with fin and tail rot is that it’s easily treatable. I agree, the one I like to use when treating this is Melafix, as it’s an all natural medication that will not affect the biological filter. Kind of smells like cough syrup or black licorice and when added to your pond or aquarium it will foam up the water which is completely natural. Same goes for the salt as mentioned, very safe to use and does not stress the fish out more like some medications do and can treat most diseases. It can also kill ich when water is heated up to 82 degrees farenheit as ich cannot live in this temperature and they die. Just need to make sure water is heavily aerated so fish have plenty of oxygen.

    Great blog! You have a wealth of information here that all pond owners and fish owners will learn a lot. Keep up the great work!


    Jamie Boyle
    The Goldfish Guy

  10. Great question. I know using non-iodized salt is highly preferred over iodized salt. They say that long-term exposure to iodine is toxic for fish. Now I know the salt used in water softeners does not contain iodized salt but I have read that they are concerns with using it. They say that the anti-caking agent, when exposed to sunlight, can generate hydrogen cyanide, which is very toxic to fish. Now I personally have not done testing to prove that this is or is not the case, but my suggestion is to use a pond salt that is specifically designed for fish and I wouldn’t chance the possibility of harming your fish.

  11. Is it true you can use the non clumping salt used in water softeners, in place of pond salt? Someone told me this, I figured I would ask the expert.

    Thanks, Guy M

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: