Great shots they look amazing.
Beautiful pictures!!!! Love the acans
Pretty good shots. When shooting aquariums, though, I'd recommend bringing up not just the tonal histogram, but the RGB histogram (i.e. the one with the three color channels) on your camera. With all of the crazy colors and crazier lighting in our tanks, it's really easy to have a well exposed photo where one of your color channels is completely blown. What you have to do is actually underexpose slightly.
Anyway, keep shooting. You're off to a really good start.