Fish are pretty challenging for me to take pics of. You either have to catch them at a moment they are not flying around, or shoot a pic of them whith the flash on. I can usually get a pretty still pic with the flash, but it doesn't look as nice as with the flash off.
As for corals, I just turn the pumps off so they sit still...hehe
Lastly, I do what Squidd said. Take hundreds of pics, and then just post the nice ones...hehe
QBall