I have five of these little guys......i love em"! they're like little "underwater puppies".....They have never been known to my knowledge to breed in captivity, so i am not sure about telling the differeces between the sexes. i feed mine krill, as well as tiny freshwater snails(crunch) and ghost shrimp. Mine are all about 2-3 inches long..if yours is smaller, you might want to break the krill into smaller pieces or give frozen brine shrimp..just swish a frozen cube around in a little water so the shrimp separate, and pour in. One important fact that the store probably did NOT tell you was that these guys really aren't freshwater fish. theynare brackish water fish which means they do need some salt in their water to stay healthy. Leopard puffers kept without salt are super prone to fungus as well as other things. I have had mine for five years and they live in my saltwater tank. It is a common occurrence with these guys in the pet store...passing them off as freshwater fish...which they are not. Also, if you have them with other fish, watch out! These guys are notorious fin nippers, and smaller fish like neons, guppies, and danios, well, just might become lunch.