I have 6, one female & 5 males.
3 are in 5 gallon filtered tanks & they get a water change once a week. One male is in a 3 gallon with no filter & every 2nd day water changes. Same with my other male who is in a 2 gallon with no filter, every 2nd day.
& my female is in a 3 gallon filtered tank she gets a weekly change.