Copperband not doing well

[Oxymoron]

I've moved him to the 50 gal. Before moving him he had started to lose some color. It doesn't look good.
He was eating brine, mysis and bloodworms before and could be hand fed within 2 months of having him. By far my favourite fish.
Its a shame he was so friendly and appeared to be doing very well 2 days ago.
Since moving him to the 50 gal he has displayed the same behaviour and is hanging out around the bottom very weak.