My first guess would be poor nutrition. How old is your tank? They usually feed off of the copipods in your live rock in an established tank. Very few eat brine shrimp of regular fish food. Im not an expert on them but i hope others will come in and help.
if its turned pale white then its dead lol
r u sure its still alive?
what are you feeding it and how long have you had it? whats your tank like? is it skinny?
Probably just got frightened. When my lights go out in my tank, my yellow tang goes really pale. Probably just a stress reaction fish have so they blend into their surroundings more. Well glad to hear its back and healthy.
Mine does the same thing. I think they turn a palish color because they have some type of mucus layer on them to protect them? I'm no expert on mandarins but that's my guess. Kinda like how a 6 line wrasse makes a web type thing around the rocks he sleeps in. When you saw him pale was it when the lights had just turned back on?
My mandarin get very pale at night when he sleeps. I have seen it a few times when he doesn't hide to far into the rocks at night. It's very creepy. When he us out and about during the day he is always nice and bright