I have had my best luck with crushed flake, cyclopeez and baby brine shrimp. once they get to about 1/4" start them on beefheart from your blender.. Just don't overfeed beefheart is very messy
crushed flakes will work fine, or you can also get "fry specific" foods such as fry crumbles, liquid fry foods, etc. one of my favorite fry foods is the spray dried krill that I get from www.kensfish.com. it is a very fine powder so even the smallest fry can eat it. just be careful not to overfeed.