definately, seperate them. You'll have better odds that way. I kept aggressives for quite some time and was surprised that my pacu did real well with the aggressives for being vegetarians. I raised two pacu from 1/4 " to one that was 18" and the other was 24" eventually they got too big for their tank 55 gal and I donated them to a pet store they keep 'em in their main tank. Good luck, if you can get the fry eating krill they'll bulk up real quick just crush the krill between your fingers to powder it a little bit. Good luck
