What Happens When a Goldfish Starts to Get Black All Over?

It is distressing and upsetting to discover that your goldfish is ill. Increasing black spots and patches are a common occurrence among goldfish, but learning the cause and solution will help you to let your goldfish live a long and happy life. In the majority of cases the blackness is cause by high ammonia levels in the water causing ammonia burns; however, in much rarer cases of pond living, the problem could be a result of a parasite.

  1. Ammonia Burn

    • An increase in the ammonia level of the water causes black spots to appear over the body of the goldfish. Black patches will also appear on the tail and fins. This is called ammonia burn and it causes a great deals of discomfort to your goldfish. If left untreated the black spots will continue to get worse and your goldfish could eventually die.

    Healing

    • While the black spots on your goldfish may look like the affected areas, they are actually a sign of healing, so your goldfish is improving in those areas. This is sometimes called Melanophore Migration. However, increasing black patches are a sign of an ongoing problem with the water which should be addressed.

    Prevention

    • Use water testing kits available from all good pet shops to ensure that the ammonia level of the water is not too high. Do not be fooled by clear water as it could still contain properties that are harmful to your goldfish.

    Parasites

    • It is much rarer that the black patches are caused by parasites often a flatworm parasite called Uvulifer ambloplitis. This is only fond in ponds, so if your goldfish is in a tank then it is unlikely that a parasite is the cause.