It's got good exposure and great color, but is uninteresting due to boring composition.
You can create better motion by trying to get the fish to swim into the picture. Try to create eye contact between the fish and the viewer, this will provide a a personal intereaction with the picture.
Also, your fish is perfectly centered. For some reason, most people find pictures that are more pleasing have the focal point of the picture, which might be the eye of the fish in this case, off centered. The "rule of thirds" provides good guidance for this.
Additionally, if you can fill the frame with the fish a bit more (by getting closer), I think it would help.
It is a pretty good picture, just picking it since you asked.
I think proper exposure is hardest to master, and you nailed it. good composition can be learned pretty easily, just take thought prior to pulling the trigger.
Take care,
John