Thanks, I tried it last night prawn in a glass, the prawn is gone and no crab, it is that big it knocked a rock over on top of my clam, i am devastated@Susan Bates how did you go? I was thinking about it, you could use a bunch of things, a soft drink bottle, a plastic food container with a sheet of cling wrap or something over it held on by a rubber band, with a hole in the top... a piece of pvc pipe with one end closed and something to stop it going back up.... I hope you get it and then feed it to your fish and coral for dinner!