What is the best food to feed lake malawi cichlids for quick growth?

I have 12 cichlids in a 55 gallon tank. i feed them frozen bloodworms, brine shrimp, & minnos. They are all @ 3" long. What can i feed them to make them bigger? They are very hearty eaters. They will eat all day if I feed them. I only feed them once a day to keep nitrates & ammonia levels low