Different kinds of aquarium pumps are available in the market ranging from small to large compressor capable of creating huge air output enough even for 55-gallon aquarium. Certain types of aquarium pump also help to drive filtration process such as the aquarium box filter and both function simultaneously to help clean the water and also creating water turbulence for aeration purpose.
Air pumps are often used together with an air stone that helps to diffuse the air into smaller pocket of bubbles for even larger surface area. To ensure optimal air output, always clean the air stones as often as possible because blockage might put more pressure and heavy load on your aquarium air pump unit. This is often blamed for pump failure even before the warranty period. Most units available in the market today are within the $20 to $30 dollar range while some higher capacity units can go as high as $50+.
When choosing for the right aquarium air pump, always bear in mind that, price is not the determining factor because your main criteria is to buy a unit that is suitable according to your aquarium size. Common mistake made by aquarium owners is to oversize the aquarium pump until it creates too much turbulence making the fish having difficulty maintaining position in the water. I would suggest getting a unit that allows you to control air output on the pump itself rather than using air valve to regulate the supply.