has anyone used a hot tub or spa heater for aquarium use? I have been reasearching and pricing Aqualogic heaters (made for aquariums) but they are very expensive. I have found some spa heaters online that are much cheaper and that i think will work. The tank is freshwater and the heater would be plumbed in-line to 1.5" pvc getting about 5500 gph. Any info is much appreciated.