a maroon clown can grow up 6".. i dont know if it's a good idea to leave it in there too long, but if you get a small one you can leave in there and provide it with a new tank while it grows.. from what i see in my tank, my maroon clown is only aggressive towards my percula and the smaller maroon clown... it's like 2 n half inches long and it is scared of a 1 n half inch damsel, so i concluded mines to be non-aggressive towards non-clowns