FIN ROT, GILL ROT, MOUTH ROT
It starts with reddening of the fins, gills or mouth and is caused by Flexibacter columnaris which is a bacteria. If not treated immediately, it will eat the fin away or create serious rotting at the mouth area. You have to take the fish out and treat the infected area with a topical treatment of undiluted Malachite green. It is also a good idea to add terramycin powder(Anti biotic) to the malachite green and you should seal it with Friars Balsam. In serious cases, you will need to cut away the infected area on the fins with a sterilized pair of scissors. Thereafter you should add an anti-bacterial treatment to the pond. Potassium Permanganate or Malachite green can be used and Acriflavine is ideal. It is also a good idea to add Virkon S to lower the bacterial count in your water. Should you encounter fin, gill or mouth rot, you are well advised to check your pond husbandry, as it is often an indication of high ammonia levels, but can also be the result of a parasite invasion or physical injury.