Well, a 100 gallon would be nicer, but since he can't see and is handicapped a 55 gallon would be ok too. The growth rate may be that way because the eyeless thing.. I think the eyeless thing was a genetic issue, maybe several generations of inbreeding, and if it is that it will affect his growth and overall health. im so glad you didn't release him! He never would have made it. the warmth of your hand may be comforting, the poor guy. Im sure being a blind frog is very stressful. That is also probably why he is in the water so much, like I said earlier, he feels safe there.