in pairs. i had two adult females together in cage for around a year and they didnt really bother eachother. one was more dominant, but they didnt fight. i put them into a bigger tank when i introduced a male and within a day and a half the one female killed the other one. you can keep them in a colony, but its not worth it because they bully each other to the point of death. i learned that with day geckos that babies, even if they are twins, they should be housed seperately. they wont always fight, but one will always be dominated, unless its a breeding pair.