I think that they are fine now as young as they are. But eventually they get MUCH bigger then the 1 in the pic as you know. And small fish are on there list as natural prey. So i think it will be fine for a while but i think in the end they will eat or attack your fish as they get older and more aggressive. But it is a worthy experiment, i wouldn't try it with the fish you have them with in fear of losing them but i might do it. Keep us updated as they grow.