I read a recent article that says that fish food needs to be re-cycled (eaten) as many as 9 times to remove all of the beneficial nutrients. Anything less than that means excess nutrients in your tank. This contributres to poor water quality. I know that my powder blue often goes after it's own as well as other fish. I have watched as crabs have torn apart snail poop also. You need to create a food recycling chain in the little environement!
I use Nazarious sp? snails, they sift substrate non-stop. Turbo grazers for live rock as well as a half a dozen margerita and other snails. Many red leg and scarlet crabs, to re-cycle the food. I aso have pulsing xenia that were growing like crazy, becasue they remove the dissolved nutients. And macro algea/ mangroves in the sump to remove it once it is broken down into nitrate.
Soo, I guess the answer to your question is not so simple.