Crister,
Less critical than the clown trigger - you should get a positive ID on your "brown spotted grouper". If it in the genus Epinephalus, it could reach a length of over two feet.
Clown triggers are highly variable in both their maximum captive size AND their behavoir. Some clowns reach 10"+ in captivity and some (like one I have now) don't reach half that size. Some people report their clown triggers are the meanest fish they've had, while other clowns are good for general community tanks. The clown I have is in with butterflyfish, dottybacks, anthias and angels - with no problem. I can't explain these differences, but I've also seen this in humu triggers. Undulatus and titan triggers are almost universally mean.
Jay