Air pumps come in all sizes, depends on how much you want to spend and how long you think you can depend on it. General Hydroponics makes a pump that they advertise as being the first and only pump designed for Hydro. If I remember correctly it has 4 outleats which you can also "T" off of if need be. Then you have the type of pump mentioned here that is used for aquarium purposes, which can also work fine I am using 4 of the fish type atm until I can afford a larger pump. Keep in mind that the more O2 you can pump into the water the happier your DWC plant will be. I'm also checking into Nebulizer pumps as I have seen numerous children need these when they are really young but as they get older they kinda grow out of whatever was causing the need for the Neb. Craig's list here I come and I bet you could find one for about $15 which is just about the same price as the fish air pump.