This is a project I've been mulling over for a while:
The "tank" is a bug keeper I picked up from the dollar store, the fishies and plants are all polymer clay. I embedded paperclips in the fish and hung then from fishing line. I used seed beads and hole-less beads for the "gravel," and glued flat marbles on the top to cover the knots where I had strung the fishing line. This project was an absolute blast!