My sons 10g currently houses 6 male guppies a giant clump of hornwort and some anubius nana. My plan was to add 6 corys when the tank stabilizes, which will add some life and movment to the tank. The guy at the fish store said I should get female guppies and could sell the excess guppies back to the store. But i have 6 males which means adding 10-20 females even with plants is a 10 gallon really up to that many guppies? How often would i need to do water changes?