Comet Colour Change

I have a red and white comet in a small raised pond of 600 litres. I have had the fish for about a year. It seems healthy as do the other fish in the pond. However in the last month it has started to develop black markings on its lip, gill and back.
Is this natural?

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Grant's Reply


Hi

No, this is not natural.

This colour change is an indication of skin damage that is being repaired.

Metallic scaled Goldfish varieties such as Comets change from their natural dull grey, to black, then gold/red/orange/white or a combination of white and one other colour.

If a Comet displays black colouration after it has fully changed colour, it is because it has sustained an injury, and is repairing the damage.

Either your fish sustained an injury, or more likely, water conditions changed dramatically at some point causing I suspect, an ammonia spike. This could have been caused by something dying in the pond or a build up of mulm.

Ammonia is extremely toxic to all fish, and burns the skin and fins.

Your fish was able to survive the ammonia spike, the water conditions have improved, and the fish is now repairing its damaged skin.

A bacterial or parasitical attack can cause the same symptoms, but normally you would have had some deaths.

Test your water for ammonia, nitrites and nitrates.

Ammonia and nitrites should be zero, nitrates ideally less than 40 ppm (parts per million).

If you don't have a water test kit, do a full water change.