I have a beta, 5 neons and 2 platys in a 2.5 gal tank with filter. how much frozen brine shrimp should i be f?

I have the frozen squares of brine shrimp and a small tank with 2 live plants and tiny fish. how much should I be feeding them and how often? This is for my 9 year old son and I do not want to over feed or pollute the tank