One tip for your fish photos. You're going to want a larger f-number (i.e. smaller aperture) on many of them in order to get sufficient depth of field. It also looks like you may have a little motion blur going on. Depending on the fish, I'm generally using a SS of around 1/200 or faster. Of course, all of this means less light, which is going to require either a higher ISO or using flash (off-camera preferably).
Lastly, make sure your focus point is on the fish's eye(s). If nothing else is in focus, 99.99% of the time, you want at least one eye in focus. . .this goes for any animal by the way, including human animals.