I have golden wonder killis (gold panchax). They are mildly gressive. Will eat fish that are not much smaller than them. Wonderful personalities. I feed mine flakes as a staple, with treats of brineshrimp or baby guppies once a week. They leave my ottos alone. keep mainly to the top of the tank, but venture to the depths once in a while. You could have a few in a well maintained 10 gallon. sexing is difiult but not impossible. Anything else?