The best food i've used is diced bonito or skipjack tuna. I just recently pulled the ones i'd had penned up for a month (was feeding them every other day till they were full) around the bahamas for two weeks, using them along the way, and even put the used ones back in the pen if they looked decent. After being back for 5 days in dirty Ft. Lauderdale water, they are all still alive, no scabs or ick on them, and the ones with the hook marks in the back are almost healed. The bonito definately helps thier immune system, rich in protein and minerals. Just my 2 cents.