They start feeding a day or two after becoming free swimmers. Frozen baby brine shrimp is what I use. It's convenient and makes the least mess from my experience. I've hatched live brine shrimp from eggs, cultured microworms, hard boiled egg yolk, crushed fish food and store bought fry food. The best has to be live baby brine shrimp, but it's a process in itself to hatch & havest so the next best thing is the frozen ones. I've bred many types of fishes, including jags and they love them.