AQUATOPs AP Series of aquarium air pumps gives aquatic creatures the oxygen they need to thrive. Available in different sizes to fit tanks from five to 100 gallons, these economical but sturdy pumps add air bubbles, create current, and agitate the waters surface to help promote gas exchange. The AP Series will help maintain stable and healthy pH levels inside your aquarium, and adjustable control knobs on the AP-50 allow you to increase or decrease the amount of air pumped from the AP-50.