Since you already have em, I'd suggest keeping them in a smaller tank in the meantime. It'll be easier to keep a high concentration of food in those tanks (but be careful to stay on top of water quality). In terms of feeding, powdered spirulina and chlorella can be bought at health food stores, and shaking up some with tank water and squirting it over them might be a good strategy. You may also want to employ a feeding dome (2liter with the bottom cut out) to further concentrate the food and give them the best chance of getting enough to eat. Some other foods worth trying would be cyclopeeze, the finest grade of golden pearls, and one of the commercial oyster egg preparations for marine fish.