ok, here is how you do it.
Get a two liter bottle, remove the label.
cut it in half with a razor blade, along where the top of the label used to be. remove the cap and invert the top portion of the bottle. then slide it into the bottom piece until both cut edges are aligned. seal it with packing tape, then bait with some frozen brine. this is sure to catch any wrasse, goby or otherwise. just let them get used to it being in the tank before you bait it.
Mobi