What causes a goldfish to turn white?

Answer 1

Other than white being the natural genetic colour of that specific goldfish nothing should make it turn white. If it has turned white then there would have to be something drastically wrong with its water. I would guess fungus is covering the fish. My advice is to do a very large water change say 90% ASAP followed by daily water changes of 20% and see if the fish gains its old colours back. If fungus is present it may also be of benefit to add 1 teaspoon full of cooking (sea) salt per gallon of water. Lack of sunlight can not and will not change the colour of a fishes scales. Lack of light can certainly change ones 'perception' of a fishes colour but that has nothing to do with the actual colour of the fish. The only things that I know of that can change a fishes colour are its current health and maybe its condition. Poor health/condition can result in a dulling of the fishes colour(s) and in some species there is a brightening or changing of colour to indicate breeding condition. This does not happen with goldfish. It has been pointed out to me by "Star Wanderer" (ref goldfish in wikkipedia) that theoretically, due to the light receptors/reflectors (chromatophores) inherent in goldfish and a natural ability to camoflage themselves to a greater or lesser degree by colour change, it is possible for a goldfishes colour to fade and become paler. I stand corrected but still find it hard to believe that a normal goldfish under normal conditions would turn white.
It's probably dead. ****Second answer= it's food may have been changed: Flamingos are born white, but eat so much shrimp, that their body assumes the pigmentation of pink.

Answer 2

It usually means that you are not providing the right water conditions for the fish. My advice is to do a water change ASAP making sure that the temperature and all the other water parameters are correct for the species of fish you have.

Answer 3

that means its sick to hell