The most nano of the nano-fish, these are about 1" long and the pair could comfortable live together in a drinking straw. I've had them for about a year; they occasionally show courting behavior but I've never seen any fry. Maybe they'll like your tank better! In theory the mail will guard the eggs in a small cavity until they hatch.

These are very shy so I would give them their own (tiny) tank with some plants and shelter. I've been feeding them strictly live food: bbs and moina; I imagine they'd eat micro or grindal worms as well.