Written by Anita Hovanesian, BAS Pub in The Daphnian Nov 1990   
Thursday, 02 July 2015 18:48


By: Anita Hovanesian, BAS

Published in The Daphnian, November 1990

Within these series of articles, I will cover some of the mot frequently noted diseases and their symptoms as observed in the Carp species.  Carassius Auratus (Goldfish), as most of us know belongs to the Carp group along with the Crucian Carp and the exotic - looking Japanese Koi.  The diseases which affect these fish all bear similar symptoms and their remedies, although numerous, are also alike for most other species of fish including tropicals.

The most common problem noted by almost all hobbyists, at one time or another, is the ragged looking tail and fins.  Water quality can usually be blamed for this.  If the pH is acidic, the fishes fins become reddened, begin to tear, and eventually appear to be “rotting off”.  The fish also may dart about and try to scratch himself against objects, as his skin feels irritated.  Neutral pH (7.0) is ideal, but Carps can tolerate down to 6.4 without showing any symptoms of stress, providing that the decline in pH has been gradual.

Most of the time, just changing some water and increasing the pH slowly by adding baking soda is all that is needed.  If no improvement is noted after 48 hours or so, a secondary bacterial infection may be at work.  High organic load in the water (frequently caused by crowding and overfeeding) facilitates bacterial growth and any animal weakened by poor water conditions tends to fall victim to bacteria, which normally occur in every body of water.

FIN ROT, as it is commonly called, has been observed in the presence of several species of Gram negative bacteria.  Pseudomonas species: (P. flourescens, granulata), Aeromonas species: (A. liquefaciens, hydrophilic, punatata, salmonicida), just to name a few.  Species of Myxobacteria may also create similar symptoms.  D.A. Conroy has isolated 2 Aeromonas species (A. punctata and liquefaciens) along with Pseudomonas putida from known cases in fin rot. (1) It becomes apparent that bacteria from the Aeromonas and Pseudomonas groups are usually the direct cause of Fin Rot, secondary to poor water conditions, mechanical injuries, and some vitamin deficiencies, such as folic acid deficiency. (2)

As the guilty bacteria mentioned are Gram negative, Tetracycline (a broad spectrum Gram negative antibiotic), would be a good choice.  It comes in tablet or capsule form and is marketed  by numerous aquarium pharmaceutical companies.  I personally prefer to use Minocycline (Maracyn II) by Mardel Laboratories as it melts easily in the water, effects Gram negative bacteria, and the manufacturer maintains that this medication does not interfere with biological filtration.  Nitrobacter and Nitrosomanas are “beneficial” bacteria, and any medication which effects them may upset the nitrogen cycle balance leading to further complications for the fish.  Another form of therapy which may work is dipping the fish in 1:2000 copper sulfate for 1-2 minutes. (3)  The use of oxytetracycline (Terramycin) has also been helpful (100mg/1 Gal water each day times 5 days). (4)  It has been suggested in several books I have read to add 2 drops of a 5% aqueous solution of Methylene Blue to the water to deter fungus attacks.

If you have tried medications, and they do not seem to work, I suggest a last resort treatment which is amputation of the affected parts of the fins.  The incision should be made above the ragged ends, within the healthy tissue, and the stump should be painted with either Providone Iodine Solution (Betadine), or Merchurochrome in order to try to prevent re-infection.  These solutions may be reapplied several times during the day, but care must be taken to prevent them from entering the animals fill structures.  The animal should be placed in a “clean”, established hospital tank with plenty of aeration in hope that the infecting bacteria are not as abundant here as they were in the original tank.  A clean razor blade or a pair or scissors would be fine to perform the procedure.

REMEMBER, if you do your water changes, check pH, and do not overcrowd the aquarium, Fin and Tail Rot will be a disease of the past.


1. Fish Pathology (TFH Publications) by Heinz0Hermann Reichenback-Klinke, p. 85

2. Diseases of Fishes, (TFH Publications), edited by Dr. Stanislas F. Snieszko and Dr. Herbert R. Axelrod, p. 92

3. IBID - p. 92

4. IBID - p. 92

Last Updated on Thursday, 02 July 2015 19:05