How to learn about fish habitat and behavior

I'm headed to Komodo in August. I know very little about the reef life there but I want to photograph all those critters. So Im trying to figure out where to look for the animals I'm looking for. Example, I want to photograph mandarin fish. So when im on the reef, where would I look for one of them? What is their behavior like? Are they skittish? What do I do to get the best chance to photograph them? I bought a reef fish guide, and I want to pick out fish to photograph, but now I need to know how to arrange a meeting.

Tell the guide your desire is to photograph a mandarin fish pair. The guide will put you where you can do this. Your buoyancy must be perfect. Stake out your spot. Be still. Plan to spend your dive not moving. They are shy, they don't like bubble noise. Tip your guide well. When you have your mandarin fish shot, tell your guide you want a shot of a flamboyant cuttlefish. Repeat as before. Tip your guide well. If you screw up the shot (these types of subjects are very difficult to shoot) tip your guide well anyway. He set you up for the shot, it wasn't his fault if you don't get it.

I don't know of any single resource that details the habits of the different sorts of marine life you can encounter in the region. In regards to your example, mandarin fish, they are especially challenging. They live among rubble, and they only come out for a short period at dawn and dusk to feed and mate. If you don't see them at exactly the right time and at the specific patch of rubble they live in, you won't see them at all. Probably the best thing to do is to figure out which of the most elusive animals you're most interested in and research them one by one.