My tank is a "AA660" set tank and I use the "set" pump at the top of the tank and a submaire pump for the 底 o侯 , but the AA set pump is very hot and make the water temp up to 31 - 32 deg and also the submaire pump is too noisy. So I change to use two external filter (one for 底 o侯 and one for general filling of water). They work very well and the water temp can down to 28 deg now.