Trap them. Get a small piece of that lightweight very pourus rock form your lfs. Cut it is half with a hack saw and hollow out both pieces so that when you pur the halfs back together, the center of the rock is hollow. Take it apart and drill small holes from the center to the outside. This forms a hollow rock with many holes to the center. Rinse the rock off very well and get a rubberband that will hold the pieces tightly together and tie a piece of fishing line to it. At night when you are ready to go bristle worm hunting, put a piece of raw shrimp (from the seafood dept. of your local grocery store) inside the rock, close it up, put on the rubberband and lower it into the tank to a place where you have seen the little suckers, and leave it there all night. In the morning, pull it out, open it up, and use a pair of tweezers to pick them out of the rock. I invented this method after other methods failed, and it works. I caught about 15 worms in 6 nights.