KollerCraft TOM Aquarium Stellar Air Pump for 30-Gallon to 40-Gallon Aquariums Air pump for aquariums sized 30 to 40 gallons Maintains high oxygen levels while providing optimal water movement to keep fish healthy Single air port outlet; 2.0 liter-per-minute air volume; 3.1 PSI air pressure rating Heavy duty diaphragms deliver years of trouble-free use