An aquarium air pump is a device that injects air into a tank’s water. At the top of a tank, oxygen enters the water and carbon dioxide is released with the help of surface agitation. Without this agitation, carbon dioxide cannot leave the water and oxygen cannot enter. Aquarium pumps influence agitation by displacing water with air bubbles. Air pumps ensure fish have enough oxygen to breathe regardless of outlying factors, such as medication’s presence in the water or photosynthesizing plant life.