Goldfish come in a variety of colors but pink spots that are not part of their natural coloration could be a sign of disease, injury from fighting or breeding, or bullying from other fish. Quarantine sick fish as a precaution and treat them to prevent the disease from spreading.
Wounds from Fighting
Small pink abrasions on your fish could be exposed tissue from a missing scale or a wound from fighting with a tank mate. Treat the injury with a commercial fish medication for surface wounds before it becomes infected or ulcerated, and it should heal successfully. Move the injured fish into a separate tank to avoid further confrontations; if you are not able to accommodate an extra tank, a friend or family member may be kind enough to adopt your fishy friend.
Chemicals and parasites cause bacterial ulcers in goldfish, and the early stage of an ulcer looks like a pink or red blotch. Excess ammonia or nitrate, inappropriate pH levels and poor water quality in general make fish more susceptible to bacterial diseases. Lesions and open wounds from fighting or breeding also provide access to a whole host of unpleasant bugs that lurk in badly maintained water.
Tail Rot and Fin Rot
Poor water quality is one of the causes of fin rot and tail rot in fish. Early symptoms are discoloration followed by fraying of the affected area. Pink spots on your goldfish’s fins or tail may be the early stages of tissue degradation and an indicator that your tank water is not healthy. Regular partial water changes help to keep your fish healthy and less likely to suffer from conditions such as fin rot.
Breeding and Spawning
The breeding season is the cause of many goldfish injuries; pink spots could be sores or open wounds. Males may fight for dominance in a tank or pond and females are often chased relentlessly by more than one admirer, which can lead to injury. Fish that get along for most of the year may suddenly change their behavior and become aggressive toward tank mates; this usually happens during the breeding season only and will pass. Consider removing badly bullied fish before they become injured and keeping them in a temporary quarantine tank. Introduce them back into the main tank after a couple of weeks.
- Fishdoc.co.uk: Bacterial ulcers a common, but difficult problem
- Animal-World: Types of Fish Disease
- Animal-World: Tail Rot and Fin Rot
- Fancy Goldfish: A Complete Guide to Care and Collecting; Erik L. Johnson
- goldfish Jim image by Sandra Brunsch from Fotolia.com