I have a white and black fish. Sometimes he is all white. Why is this?

Answers:
i have a striped (black and white fish) if this is what yours looks like then its called like a criminal or prisoner or something like that and mine turns all white when it gets startled, depending on the mood the black can darken or get lighter and when they are all white they are upset

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If he is all white at night, that is normal. He may also be scared or mad. You have a pretty special fish.

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Probably depends on the fish - most fish change color slightly when stressed. I have a tigar oscar and when he is in a good mood he is a striking black and orange. When he is stressed, he turns almost totally gray.

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Honestly, you should try to find out what species of fish you have. It's rather difficult for people to help you when you're ignorant of your own fish.

Fish change colors for multiple reasons. Bad water chemistry, stress, camouflage, breeding.. I suggest you find out what fish you have and then look into color changing for that specific fish.