I had a picture many years ago (might even be in the archives here on MR) of my brain coral eating the empty shrimp molt. At first I thought the brain was eating the live shrimp, until I noticed the shrimp in his cave and determined he had just molted.
I've read reports/theories/thoughts about food in a reef tank being consumed and re-consumed 4 to 5 times (maybe more). For instance, fish eats pellets (1), fish poops and Royal Gramma eats the poop (2) (I've seen it), Royal Gramma poops and falls to sand where crabs eat it (3), crabs poop and snails devour it (4), snails poop and it continues to break down and pods go at it (5). After the pods are done it continues to decompose and the denitrying bacteria consume it (6).
Amazing stuff our enclosed systems are........
Russ