The focus does see a little off, which is not that unusual in a water filled tank with moving creatures. The colors are great and the lines and patterns around the critters are really interesting.
Aquarium shots to me always seem to be rather weak photos. To do those shots well, you have to have perfect lighting as well as a proper room to do it in. Also, you need to have the proper glass on the aquarium so you don't get all those strange colors. I'm not the expert in the right way to do it, so can't offer any advice to you. I just know it can be done, as you see some rather spectacular shots every so often.
This takes patience to wait until all the fish, etc are in the right place. When you are combating glass, water, and the light, your lens has to be right on the money. As I recall, the Zo has had over time some rather good aquarium shots posted that might help you get a better idea.
In my estimation, this is a rather weak shot. The fish/shrimp are poorly shown, the light isn't good on them and they aren't sharp. Just keep trying to do this better and you will eventually get there. Try different lighting and see what happens. i think you are using just the florescent bulb in the top of the aquarium and that just doesn't cut the mustard.
The trick to good photography is to learn where to point your camera and when to push the shutter. The EYE is more important than all the technical stuff.