was that question re the fluval filter mate? Its a cannister that sits under the tank, the tank water is syphoned out via one tube, that water then passes thro the filter media in the cannister and then pumped back in via an outlet hose. I prefer this type, purely cos it saves me keep lifting the canopy when I needed to clean/change anything. The only thing you have to be careful of with the fluval is to make sure the large o ring is kept wet and seated when you replace the motor housing, had the bloody thing leak once, nightmare!
Most people recommend the eheim filters, the media is fairly cheapish, and you can get spare parts for them quite readily if need be, but a bit beyond my budget, but one day!