Elemental Air Pump

I've never heard of an air pump output stated as gph. To most folks that means gallons per hour. Air pumps are normally in CFM or CIM Cubic feet per minute or cubic inches per minute. GPH ,makes it harder to compare to other pumps.
Personally I use a Pondmaster AP100 but I've got a lot of tanks. The pump itself is quite. The air filters in the tanks not so much. But they aren't in my main house so it's not a problem. In the house I use the Tetra pumps. Unless the wife vacuums and moves them so they don't sit flat they are dead silent.
 
Is it an Air pump or water pump?
 
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