An air pump isn't always required for your aquarium to function properly but it assists in the operation of certain air filters, provides additional oxygen for your aquarium's inhabitants and is necessary for the performance of certain aquarium décor. The type of air pump you need is contingent upon what you'll use it for. Once you determine the role your air pump will play in your tank, it's simple to choose the right pump.
Role and Function
General purpose air pumps provide aeration and are necessary if you're using air stones or an under-gravel air filter. Purchase the pump based upon the tank size, and read the manufacturer's instructions to determine proper installation. If you're using your air pump for multiple purposes, or to power action items such as a sand fountain, spinning wheel or other movable-part action décor, you may need a more powerful air pump. A high output air pump is necessary for very large aquariums or ponds. Air pumps are also available in battery-powered models, which may save the life of your aquarium's inhabitants in the event of a power outage.