Well, after getting a few reports we consulted with an ethologist about wrasses entering the pumps and she said that they dart into caves when frightened and they can accelerate fast enough to enter a running pump. They think the pump opening is a cave, especially when it is in a stream rock and the result is wrasse puree. We started working on screens for all the pumps for this reason, the fairy wrasses are the main risk. They do reduce flow and I have only known of a wrasse to enter the pump on 3 occasions.