yellow tang has little white spot on him , is not a dot its like a little ball or a cottage cheese looking spot , any ideas on what it could be ?
4ft with 3 ft sump
I kind of sounds like it might be the start of something, a picture would be helpful. Do not panic, most things will take care of themselves with good food and good water quality. What are you feeding? How is the tang acting?
if it is MI, then its already in you main, its too late for a qt, moving him will just add more stress, what size of tank and what kind of tank mates. If you do not have the proper environment, as soon as you put him back in, he will outbreak again as it is in your main alive and living
Tangs stress very easy, so yes move him back. It is hard to tell by that picture, get one that is not so close. From that picture it looks like a grain of sand stuck to it. Just remember diet plays a big role in our fishes health, you would get sick really fast if we put you in a glass box and fed you nothing but potato chips. We will figure this out...
Here is a good article on MI and myths, the guy that wrote is well known in the industry, I would just leave him in the main, good food and mainteance' as long as he is getting picked on, your tank is a little small for tangs, might be a contributing factor to the outbreak