I use a clear 2 liter bottle. Just put a little of your sand in it and sink it to the bottom with a small piece of frozen shrimp in it. After a while your eel will have found his way into it and eaten the shrimp. Let him get away with the first time, just so you don't have to wait around for the eel to figure out how to get in the bottle. The next day just put another piece of shrimp in it and sit back. My eel went right in within a couple of minutes. I just reached in and put my thumb over the top and pulled him out. My firefish are safe again!