Composition - My first impression is that this is a tough, tough shot to pull off. My best picture of a fish was one that barely moved, ever. It was really stationary and it came out decent at best. I think there are 3 definite reasons why the composition of this photo didn't work as well as it could've. The first is the fish are facing the wrong way. If they were facing into the camera, add about one point. The tilting of the photo is not helping things either. I think that's strike 2. I see you apologized for it in the comments, but it doesn't help in the voting. You did pick a very worthy subject though. I've always like the color of these fish and how big they look with their front fins and kind of big heads.
Technical - The third strike is the focus. It's reasonably well focused considering the shutter speed was 1/30sec. This alone makes it tough to focus. Not to mention that the fish were probably moving. If you could've made this crystal clear, you could've added a little more to the score. The exposure is just right. The colors are very vivid. A very clear pic for ISO 320.
Overall - Fix those 3 problems and you have a very good photo. Easier said than done, I know from experience. In my own small tank at home, the last time I tried to photograph my fish, I put a 1000w light kit shining into the tank along with the normal fluorescent lights that are already there. It worked pretty well all things considered. So I think the flaws of this photo are pretty obvious, but not easily fixable. This is a tough one I know. good luck in your future challenges - Inspzil
lionfish! I almost submitted these myself, but the little buggers kept moving about and I didn't get a clear shot. I would have preferred is yours were coming toward you instead of away as it leads us out of the frame.
I know photographing into an aquarium can be difficult. The Fish on the left is in focus, but since it is swimming away I would have prefered that the other lion fish had the focus.