depends on the reef you want to keep.. if you have lps, you can just about all but forget about angels.
if you don't they're pretty much ok.
IF your reef mind thinks it needs snails, hermits and such triggers won't fit in.
No real one answer..
as in everything that lives on a reef consumes something found on the reef.
If you go on most of the sites that sell fish, they tell you if they are reefsafe... www.liveaquaria.com is one www.saltwaterfish.com is another and there are a bunch more. They will tell you, if you click on the fish you like they will say... but i would check more that one site, cause some of them have different info about what is reefsafe and what is not.