I used a small version of the plastic soda bottle fish trap, instead of a 2 liter bottle, used a 20 oz. plastic pepsi bottle. Cut the top 1/4 off and invert it and glue it to the inside of the bottom portion of the bottle. Add a little scallop, squid, shrimp of your choice and place in trap. Place in bottom of tank near where the crab lives and take out the next morning. I tried using the glass jar method and my fish and cleaner shrimp just thought I was serving them up a treat in a dish. Also with the bottle method you can almost lay it horizontal depending on the size of the crab you are trying to catch. Good luck. I've been there. I now have a gorilla crab and whelk tank as my refugium.