NIck pretty much covered it. In a 40 I would be careful how many fish you add, and would stick to species that stay small.

The dwarf Angels Nick mentioned can get a bit aggressive, and if you do plan on keeping corals (after going slow...), are known to be coral eaters. They are nice for a fish only tank though.

One of my personal favourites, and quite coral freindly, is the Orchid Dottyback (Pseudochromis fridmani). They stay small, and are quite active and curious.

Fred

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