You've done a pretty good job! The shape is a good match to the reference you were using and you got some nice details worked into the fins. If you're going for realism, I would suggest practicing with a little bit of shading. Since you're looking at a photograph, knowing where to shade is as easy as knowing how your lines are suppose to curve. I would suggest practicing shading by using a blank piece of paper and shading bars going across it. Start with heavy/dark shading and go to light, then switch it up and go from light to dark. The goal is to try to transition smoothly from one to the other. Practice until you feel like you have a pretty good handle on the smooth transitions and on how much pressure you need to get the depth of shading that you're aiming for and then give it a shot on your fish! You'd be surprised how much a few touches of shading can improve the overall appearance of your work.
Also, as far as the color goes: I would suggest adding a very soft green in with the blue to better get the blue/green effect that your lovely fish has.
Last edited by zombieaddict; 12-06-2013 at 10:16 PM.