They do, but its impossible for them to hunt in the open while they are swimming around, they need some object to sit on and wait for a fish to get close, polys are not fast hunter in the open water ive seen it multiple times before when my LJ tries to take down my SD and bala shark, with a open no decor tank that the other fish dont need to swim in the bottom its nearly impossible for a poly to catch a moving prey even with light off.