Got a yellow tang week ago tank is 30 gallons I know its too small ill be upgrading soon. but he only comes out from behind the rocks when the lights on and turns brownish with his white stripe. when he hides. also how often do I feed him. I have seaweed and flake food?
He will become stressed, in that small a tank. 75 gal min is suggested.
+1 on a bigger tank.
Feed him twice a day with frozen food and give him norI once every two or three days.
Your time will need to be consistent. Mine opens at 10 AM and closes at 10 PM (timer) so all the fish comes out when the lights are on and go into the rocks to sleep when lights are off. The yellow tang will turn brown with the white stripe when it's sleeping or stressed.
AS atp mentioned the colouring is due to stress watch him for ich as stress will bring this on , Imo I would upgrade sooner rather then later ,