These deep water pumps provide air to even the deepest tank, down to 96" depth. An excellent choice for use with a multiple tank, multiple airstone application. They are also an excellent choice for driving protein skimmers.. Find the Model you need based on your aquarium depth in inches and number of air devices you have in your aquarium. DW 12, for tanks of 12" to 24" with 1 to 2 air devices. DW18, for tanks 18" to 36" with 2 to 4 air devices. DW24-2, for tanks 18" to 48" with 3 to 6 air devices. DW96, for tanks 24" to 96" with 2 to 6 air devices. DW96-2, for tanks 24" to 96" with 3 to 10 air devices. All TetraTec pumps come with a limited lifetime warranty so that you and your fish will never have to depend on another air pump. Info from Q-pet.