I built a powered gravel vac this week-end that used a second hand Fluval 403-yes a 403, not a 304...
Intake is a 1" clear to a male hose thread fitting, then I attached a connector onto the gravel vac tube(1/2" adaptor to hose fem). The output of the canister is attached to a hose 'y' fittng then to a length of hose to water the front lawn... I had to use the Y fitting to allow me to start the syphon, as these older canisters needed a bit of work to get started when dry, but a Cascade or similar has a built in sypon...Not too sure what media is in this, but all you need is a bit of mechanical media in there to keep out any debris from the motor. Simple and I was able to do a water change in under an hour on about 365 gallons of water split across 6 tanks.