A Closer Look at Tail and Fin Rot – Part 2 (Treatment)

As explained in “A Closer Look at Tail and Fin Rot – Part 1 (Symptoms & Causes),” tail and fin rot is a symptom of a serious bacterial infection.  Understanding that basic point is key to understanding the reasons behind the treatment.


Affected goldfish need to be removed from the tank and put into a treatment tank.  (Some people refer to a treatment tank as a hospital tank, isolation tank or quarantine tank.  These names are interchangeable.)

Any small tank fitted with a box filter and containing no ornaments or plants is suitable as a treatment tank.

The reasons for isolating the affected fish are:

  • to help prevent the spread of secondary infections to other fish in the aquarium
  • because one of the treatments is an antibiotic that will either wipe out or decimate the good bacteria population on biological filters
  • it’s easier to keep treatment tank water in tip-top condition
  • there is reduced (zero if it’s only one fish) chance of fighting or bullying causing further problems

The only other thing to do before commencing treatment is to raise the water temperature a couple of degrees in the treatment tank.  The bacteria that cause tail and fin rot prefer cooler water.


There are two separate parts to successfully treating tail and fin rot: one is to treat the main tank, the other is to treat the affected goldfish in the treatment tank.

To treat the main tank, change the water, test the water quality and make any improvements that are necessary, and make sure the goldfish are receiving a healthy, balanced, nutritious diet.  Also make sure there is no rotting plant or food material in the gravel at the bottom of the aquarium.

To treat the affected goldfish, put a teaspoon of aquarium salt in for every gallon of water in the treatment tank.  Salt is a natural antiseptic and has wound-healing properties.

The other treatment, as already mentioned is antibiotic.  The most common ones used to treat the bacteria behind tail and fin rot are tetracycline, chloramphenicol and oxytetracycline.  Dosing instructions will be provided with the antiboitics, most of which come as commercial brands with user-friendly labels.

Obviously most treatment tanks are small, and some of the dosing instructions may be for larger quantities of water.  A handy tip is to pour 10 spoonfuls of water into a container, then add the antibiotic as stated on the label.  To dose the smaller quantity of water in the treatment tank, just use the same spoon to dole out 10ths of the large dose of antibiotic, until the correct amount is in the treatment tank.

One other handy tip is to completely ignore the length of treatment stated on the label.  Continue the treatment until tail and fin re-growth is noticeable.  Stopping treatment before this may mean the bacteria have been knocked down, but not finished off.

One proviso is that if the treatment has gone on for 3 times the length stated on the label, it is probably not working.  When this happens, change to a different treatment.

At all times, make sure the water quality in the treatment tank is what is should be.


No secrets here.  Keep the water quality good, feed a healthy balanced diet, don’t overfeed, don’t have too many fish in the tank, keep the temperature steady, quarantine new goldfish, and make sure all the goldfish in the aquarium lead a stress-free life.

11 Responses to “A Closer Look at Tail and Fin Rot – Part 2 (Treatment)”

  1. lmccleaf Says:

    Urgency. We’re leaving the country for 2 mos on Nov 19th. On day 5 of maracyn for fin and tail rot–no change. Water: ammonia:0, nitrite0, nitrate0, & ph 6.6–maybe result of maracyn–typical is 6.8-7.0–55 gal freshwater tank, 15 community fish. 2 clown loche, 2 small gray angel fish with beautiful sheer tails, 1 red tail shark, 2 golden guppies, 3 red tail sword, 1 plecostymus, 3 tiny sucker fish. Clown loche and angel fish are only ones infected. 1 redtail sword had popeye but it cleared up. My mistake: Did not change carbon until day 3 of treatment. Also have an eheim 2213. Recently changed filter pads . Also have a nitro sorb pouch in cannister. Just put in recommended salt quantity and raised water temp.

    What can I possibly do to completely clear this up before leaving. I don’t know of anyone in this area to be able to do a water change or step in on my behalf. Our house pet sitter know nothing other than feeding and can put in or remove carbon.

    Thank you for your response and timely response


  2. sandrar Says:

    Hi! I was surfing and found your blog post… nice! I love your blog. 🙂 Cheers! Sandra. R.

  3. Dana Says:

    I have one four-year-old goldfish that is quite large. He has been extremely healthy all this time. I am very careful about water quality and feeding. Even so, he has presented with red streaks on his tail fins. I am assuming that I am seeing tail and fin rot, although the no other fins appear to be infected. I will attempt the salt treatment, using the large tank he is in. There are no other fish in his tank. If anyone out there knows of any other reason why my old man fish has red streaks on his tail fins, please let me know. Thanks for this site, it has been a great help.

  4. Dana Says:

    My four year old very large gold fish has red streaks on his tail fins. I am assuming he has tail/fin rot and I will treat him with the salt as prescribed. Thanks for this site, it has been quite helpful. If any one out there knows of another reason why my goldfish has red streaks on his tail fins, please let me know.

  5. Kelly Says:

    I bought 2 goldfish at petsmart and I didnt realize till I got home that one of them had badly torn up fins and rough looking scales now I am seeing small red sores on it’s body and he has been swimming at the top of the water alot. I changed the water but that created no change. What can I do? I have found several different illnesses but he is lacking other symptoms of those illnesses. What may he have? and how can I treat it? should I seperate him from the other fish? PLEASE HELP ME!!

  6. Kelly Says:

    I am sad to say that minutes after I posted that last question (above) my fish died he is in a better place now. But thanks to anyone who thought about helping.

  7. Courtney Says:

    Please help. My dutch lionhead goldfish is missing scales and a lot of tail. He/she can’t swim and we have removed him/her out of the aquarium so my other fish can’t get infected. Is this tail/fin rot?

  8. Ian Says:

    Got our first goldfish for my son 3 weeks ago. After a week we notice it had got fish lice.

    Removed it – complained to shop – said we would see how it went – got another one… Treated fish with interpet #12 anti-crustation immediately and prepared a hostipal tank.

    Fish now in hospital tank but has two distinct & growing streaks on the dorsal fin where I found the first lice.

    Had the fish out for a closer look and it does not look like the lice (smaller or otherwise). It looks like it is within the fin itself.

    I suspect some secondary infection from where the lice were attached.

    It does have the charateristics of fin rot, but the blackness is like a streak in line with the bone in the fin and radiating from the back of the fish for a 5 or 6 mm.

    There is no los of fin at the edges.

    Water quality not what you call great – struggling with the fact the main tank seems to be infested with lice and need to get him isolated…

    Any clues on the “black streak” and any quick fixed to get the nitrate level down?

    I had used the filter from the main tank in the hospital tank because I understand the bateria is in the filter and thought that would help.

    Many thanks

  9. sunny lakewood Says:

    To kelly,
    Kelly it sounds like one of your fish has fin rot.fin rot is when a bacterial infection eats away
    At the fins tissue.if it is caught early enough,you can treat it with Melafix.melafix helps to quikly
    Regrow damaged fins.if the fins at the base of the tail get eaten away,it is too late.your fish will die becase the infection is inside the body.there are many types of medacine that cure fin rot.melafix does NOT cure fin rot,it simply regrows the fin. Age-12

  10. Isabella Says:

    My gold fish died from fin rot don’t mix suckerfish with goldfish.my goldfish was named Stan and he was important to me.i got him from the fair Stan lived for two years.he use to live in a bathtub for two days he lived through stuff that could kill him.i realized his tale and started cryin.then I got his and he use to get happy, whenever I showed his food container but he didn’t so I got the food out and wasn’t happy still.that night on August 8 2012 stan died he was on is little sigh in his tank laying kinda like a back bend.now I have a new fish named Stan and he has a girlfriend now they have little eggs I fish Stan was here but he will always be with me forever and I no he’s in a betters place

  11. kailey Says:

    this helped me so much with my research.

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