Sorry this is my first post and don't really know what I'm doing :/
My angelicus catfish is starting to turn white

He is in a temporary holding tank that was properly established that is 56 gallons. He's with live plants, hiding places, filter, heater water is good. He was with my oscar in the bigger tank but when I found bite marks and scratches on my oscar I decided to separate them. He has been with me for 5 months now and it just started...please help!