I have used them several times...In the spring several weeks after crappie, bluegill, etc. have spawned, I would hang the minnow trap from the ramp to our dock, better probably to place it in the shallower water along the ramp, but have trapped minnows in all depths. I used soda crackers inside the trap and also if I see small fish activity close by it's good to just throw a few crumbs of crackers/dry bread around the trap. Most of the finny swimmers caught were small bluegill fry...1 1/2 to 2 inches, which work well for crappie, but better for white bass, bass or catfish.
One evening, wanting to trap crayfish, I put in several crappie heads from fish caught earlier. The next morning I pulled up the trap and there were 2 or 3 small water snakes in the trap. They were of course dead, so that was the last time I did that!
CrappieHusker