most tangs grow slow, not all. I think trophs are one of the few that do grow at a normal rate. MY brevis fry were older and bigger than my salouis fry when I got them. The salouis have out grown them by an inch already. (in 2 months). I think that comps and calvus grow the slowest.
Also, everyone that I talked to who has puffers and cichlids, suggested not to mix the two. It would be bad after he reaches 5-6 inches.... I know its said that your question has actually been part of my daily conversations.