I haven't had much success with crappies on tip ups, mainly because the way they feed. Crappies will usually take a bait from below and then sit there.....net result is your tip up doesn't go off! I have found that crappies will end up swallowing the hook before setting off your trap, and that isn't good if you plan on releasing them. Besides, you can catch a ton of them with a jigging pole once you locate them.