What's wierd about marine fish is the fact they will fool you into thinking they are dead or dying. Don't get me wrong, when they are dead or dying they will have a certain look to them , and it helps greatly to do a lot of research about your specific types of fish, but like a porcupine puffer, humu trigger, clowns, etc.. They tend to get lazy and sleep in all sorts of odd positions..upside down, on their side, facing straight up and sometimes they will stick themselves to intakes just so they wont float around and expend energy to stay in one place. At first you will think something is wrong but after you get used to your fish, you'll understand them, their habits, and their personalities.
As far as feeding and i'll mention i'm no expert, fish will eat when they want. If they are hungry they will eat, when they arent, they wont eat..which doesnt happen very often. I just picked up my first clown two nights ago and fed him the next day, and to his satisfaction, he ate like a pig. Same with my snowflake eel, the very next day he ate like a king.
HTH
Jrittz