It is ridicules to compare an omnivore organism (us) with specialist. You do not feed your cat and dog with only vegitarian food and not your cows with hamburger. Its the same with many reef fishes - they are specialists - you need to feed them with the right food. A vegeterian fish - like tangs - have much longer intenstine than other fishes - feeding them with meaty foods will cause difficulties for the whole organism.
Sincerely Lasse
Sincerely Lasse