This is how naive I am...

When I orig. read the subject title, I thought it was about those pieces of *real* glass shaped like fish, etc and with pretty colours injected through them. They are attached to baubles with varying lengths of clear line to make them float.

Most ppl. get a few in a glass vase to brighten the place up but I had an empty tank that I filled with them - fish of sundry shapes and sizes, divers, crabs, dolphins and even a submarine.

Of course it does not look at all realistic but it brightens up the room it is in and is so much easier to maintain.