Fin Rot

Fin Rot is a form of bacterial disease that eats away at the fins of koi and goldfish.  In extreme cases the fins can be eaten away all the way to the "meat" of the fish. 

How to Recognize, Treat and Prevent Fin Rot in Your Koi or Goldfish Pond

Fin rot is a very common ailment in both koi and goldfish and is usually a sign that there are other problems or stress factors present.  Anaerobic bacteria eats away at the fins and can rot the fins all the way to the meat of the fish.  Usually, once the fin rot is stopped the fins will grow back without leaving scars.  If the fin rot gets all the way into the flesh of the fish, however, the fins affected will not grow back.  Think of them as fingernails.  If the finger is gone, the fingernail will not grow back.

Stress factors such as parasites, poor water quality, over-crowding, and injury will weaken the immunity system of the fish.  When this happens the fins may be the first area of the fish to show the damage.  We look at fin rot as more of a symptom than an actual disease in itself.  Though not as serious as ulcer disease and mouth rot, fin rot is your cue to get rid of what is causing aggravation to the fish.

Recognizing Fin Rot

Fin rot is the easiest symptom to see.  The edges of the fins are ragged, torn and missing.  Often the areas where the rotting is occurring is red and inflamed with infection.  Left to run its coarse the fins can be eaten totally away leaving the fish unable to swim properly and often causing death.

Sometimes fin rot is accompanied by fungus that feeds off the dead tissue left behind by the infection.  If the cause of the fin rot is taken away the fungus should go away on its own but we do have fungus medications that can relieve the symptom quicker.

This poor little goldfish has fin rot but it is complicated by the addition of fungus feeding off the dead tissue.

Treating Fin Rot

First of all, test the water for ammonia and nitrites.  Sometimes the major factor causing the fin rot could be as simple as poor water quality.

Then - we need to determine that parasites are not causing the fin rot.  If you've added fish within the last month before the outbreak or if your koi and goldfish are exhibiting symptoms of parasites immediately begin treatment for parasites using the Parasite Pak.

Once the parasites are treated the fin rot may clear on its own.  If not, we must treat for fin rot.  Bad (anaerobic) bacteria causes the infection.  It is naturally present in all bodies of water though some ponds are more ideal for breeding it.  Melafix is a less stressful treatment that can be used as a tonic that helps get rid of fin rot.  A salt treatment will also help stop the fin rot and boosts the production of the fish's natural slime layer and that, in turn, helps build up his immunity to bacterial diseases.   

It's not a bad idea to treat the whole pond with a bacterial treatment such as FuBa Fix, especially if the fin rot in your koi or goldfish is accompanied by fungus.  Do NOT treat your pond with two different medications at the same time!  Remember not to allow any bacterial treatments to flow through your biological filter or you will end up without a functioning nitrifying cycle.  Bacterial treatments do not differentiate between good and bad bacteria.    

For those fish that have advanced fin rot or it is accompanied by fungus a topical scrub or dip is recommended.  The best thing we've found for any bacterial disease, including fin rot is Tricide-Neo Ulcer Dip.  Unfortunately some fish are just too weak to withstand the harsh treatment.  For those fish we have Lil' Dab-a-do Ulcer Scrub.  You may be able to get by instead with just scrubbing the fins with Anti-Bac Scrub if the fin rot is not advanced.

If using a scrub or dip you must be able to handle the fish every day for about a week so if you have a hospital tank it will make the treatments a whole lot easier on you and the fish.  You need not quarantine any fish with fin rot (unless you have the availability of a hospital tank) because unless a fish's immunity is weak (or there are other stress factors going on such as water parameters are bad or parasites are present) he shouldn't break down with fin rot by simply swimming with an infected fish.

Emergency Procedures

1. Test the pond water for ammonia and nitrites.  If you have readings of either, do a major water change and follow directions for boosting the biological filtering in your pond.
2. Check for the presence of parasites and treat if necessary.
3. If the fin rot is advanced, use Tricide-Neo or Lil' Dab-a-Do.
4. Treat the whole pond with Melafix or FuBa Fix if several of the fish show signs of fin rot.

What to Expect Next

If the fins begin growing back and the fish seem healthy it appears that you have successfully gotten rid of the fin rot and whatever factor was present to contribute to it.  There should be no residual effect from the fin rot unless the fins were eaten completely down to the flesh of the fish.  Many fish have lived long lives with half fins or missing fins. 

Preventing Fin Rot

Keeping the fish healthy is the trick to fighting fin rot.  As a precaution in spring we like to feed our fish nothing but triple antibiotic food for two weeks.  This builds them up and helps them fend off any stress factors that may crop up.  Another precaution we like to take is to treat the pond in early spring with a Parasite Pak - just in case... 

A clean pond is monumental with helping stave off any type of bacterial disease including fin rot.  Do not line the bottom or the pond with rocks to give junk a place to hide and grow anaerobic bacteria. 

More Information About Mouth Rot

• How to Prevent Spring Disease Outbreaks in Koi & Goldfish
• Battle of the Bacteria
• Tricide-Neo Antibiotic Dip for Ulcer Disease in Koi & Goldfish
• Melafix - Helpful Tonic for Bacterial Problems such as Fin Rot on Koi and Goldfish

Items You Might Need:

Tricide-Neo

Lil' Dab-a-Do
 

FuBa Fix

Triple Antibiotic Food

Melafix

Doc's Pure Salt

Ammonia Test Kit

Nitrite Test Kit

Doc's Prescription
Anti-Bac Scrub

Parasite Pak

Know Your Gallons!

Heavy Duty Water Meter

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