surface agitation is what helps with oxygen exchange... an air pump doesnt actually put air in the water, it just disturbs the surface, which helps with getting oxygen in the water... I dont have air pumps on any of my tanks, my filters provide enough surface agitation... If you dont have much surface agitiation, you may want to consider a spray bar if you run a canister filter or a wet/dry setup... i just think that air stones and wands/bars/etc make the tank look all phony, and take away from the natural look... remember, lakes and rivers dont have air pumps in them, the wind and currents and waterfalls (if they have them) do the work, same thing as filters