They have a "safety" guard built into it now. Not sure if they did then (I have the Gen 2 model). It keeps the fish from getting into the lower crevices and the flow of the water as you close it pushes the fish out of the higher ones.
Though last night one little bugger figured out how to get under the guard as I was putting the plants in. Had a fun time pulling the guard out and coaxing the fish back out, lol.