Clean glass is a MUST. IMO, try to focus on one piece. I'm not that experienced with photography, but you should try to focus on one piece of SPS or a colony of zoos. Maybe get a top down shot of the clam. Here are some I did with my point & shoot when I had my tank....
here are a few more. Cleaning the glass before a marine shot is pretty much marine macro 101. Shooting thru glass and water is a total learning curve. I specialize in marine macros
I love the composition of this umbrella coral
This image has a few pest that are not wanted in a reef tank, but interesting too look at