Just saying "you need air in the tank" is a bit misleading to people not well versed in the process of CO2/02 exchange in an aquarium.
You don't "need air IN the tank" as in needing air pumps/bubblers/powerheads, etc... putting air bubbles in the tank. Air bubbles in the tank are not what your fish “breathes.”
What you NEED is for the surface tension of the water to be broken. Fish expel CO2 and take O2 from the water. This CO2 is then in the water column until it reaches the surface of the water. If the water tension is not broken (rippling, moving water at the surface), the CO2 will not be exchanged at the surface for O2.
So…..I don’t care how you do it, but you just need to agitate the surface of your water. This can be done with your filter returns, powerheads, bubblers, or whatever. And if you don’t like bubble jets from a powerhead shooting into your tank, you can get rid of it. Just make sure the surface tension of your water is agitated so that CO2 can be exchanged for O2 at the water surface.
Fish DO NOT need bubbles in the tank. They don’t “breathe” air bubbles.
A decent introductory article on the subject:
http://www.ratemyfishtank.com/articles/104