So then the rule of thumb would be dont put any small fish in that a semi aggresive fish could get in their mouth... So peaceful and Semi should more or less get along as long as they are not too small?
General rule Triggers/Groupers/Lions/Eels/Damsels are aggressive + others just do some research on aggressive fish. Peaceful Tangs/Chromis (some)/Wrasse (some)/butterfly/Angel (1 per tank). Good luck
