Right, I have just tried to use the powerhead. I placed the powerhead into the intake (without the end strainer), keeping both underwater. The cannister filled with water and bubbles came from the outflow, but only when the powerhead was inserted. When I took it out there was nothing. A full canister but no syphon. I turned the filter on and all I get is the very noisy rattling sound. There was no suction and nothing coming out of the outflow..