Yes, that tiny you will need fruit flies. You can seed your tank with isopods and springtails, which can be bought online. Make sure you have leaf litter for the little guy, there is nothing these frogs love more than foraging through leave litter for isos and springs. If it's that small, you won't be able to sex it yet. You will know if it's male or female depending whether or not they call when fully grown. Keep in mind, they are very loud callers! They will call consistently all night at times and it is very hard to get used to and sleep through. My peepers also liked earthworms chopped up very tiny, but didn't go for them until they were comfortable with me and associated me with feeding time.