Tilapia will eat anything, so live feed isn't really needed. When mine are tiny I feed them crushed flake food, which is quite inexpensive. As they grow I change them over to floating granules, and finaly to pellets. If you have access to duckweed, they can feed off that once they are 1/2", which just takes a few weeks.

If you do feed brine shrimp, add a couple of tablespoons of sea salt per gallon. I don't advise this if you are growing plants, but in fry tanks it does a couple of things. This protects the fry against a lot of diseases, and the brine shrimp can live for days without making a mess.