I used Molly's templates for all my fish, except the jellies. I got the idea to use ric rac for those, which was much easier and more stable - I don't have much wool felt on hand, and the craft stuff just doesn't hold up well when it is cut into thin strips. All of the fish have a velcro backing, so they can be moved around.
I also made one of the cute pieces of coral, but it somehow got lost in the sewing process. Sad! Hopefully it will turn up, and I'll add it to the page.
The "sand" is a felt pocket and the seaweed plants are made up of a funky ribbon that I clipped apart. I also threw in a raffia/bead trim for another type of plant and to add texture. My friend Megan gave me the trim a year ago, and I never thought I'd find a use for it. :)
Check out the Purl Bee for some awesome felt aquarium templates!