A lot of persons ask this question as it is believed that a water pump can also pump air in hydroponics. It is erroneously thought that all that is needed is to pump a substance, so, water pumps should be able to pump air. This is NOT true. A water pump can not pump air in any effective way at all in hydroponics. One thing with water pumps is that they are built with higher viscosity and density to pump water. The viscosity is like 1000 times greater than that of air pumps. If you use water pumps to pump air, they would get destroyed because the lubrication and cooling of water to prevent dry heating is not available. More so, they(water pimps) would not even pump air effectively. Air pumps are the best for pumping air. Do not settle for less.