I use a Rio 600 RVT pump (http://www.marinedepot.com/Taam_Rio_RVT_%28rejuvenating_venturi%29_Powerhead_Pump_Fixed_Flow_Aquarium_Powerheads-TAAM-TA3191-FIPHFF-vi.html) to power my CO2 reactor, I like the pump for its low noise and venturi configuration, but what I hate about it is there is no protection from the impeller. So far I've lost 3 fish because they managed to get too close and said pump turned into a meat grinder :-\
I've tried sticking a piece of foam in front of the intake but however coarse, it makes for a noticeable restriction on the pump's flow (unless I clean the foam on a regular basis, which is a pain because of where it's located in the tank - hard to reach spot, hidden behind plants and whatnot)
Does anyone use this pump, and found a good way to protect fish from the impeller ?
I have never used the pump but one option would be to use the nylon screen around the propeller. I have used this to keep my shrimp from becoming filter media.
Fixed. I bought little cartridges (http://www.petsmart.com/product/index.jsp?productId=4133182) of carbon for 3.49$, emptied one, cut it in half and glued it over the pump intake. It's like a little perforated plastic cover, works perfectly and easy to clean, too.