[monocus]

they look like upsidedown jelly fish-they will grow to about 5/8 of an inch and are completly harmless-they feed on light and plankton but nothing i know of will eat them.if you have bright enough lights(metal halide or led)you can breed them and sell them to your local store.they will come back every year.i use to have them before my tank crashed and they are fairly interesting.they start out on a stalk under the rock and will eventually turn a translucent blue