Just about everyone on here will tell you to run air to the pond except me. I say run electric. Unless you keep your line on grade from pump to water, any dips in your airline will collect condensation. Without the right site, how do you take a buried airline up to a valve box or into the water without making a big P-trap in the line? That P-trap full of water will increase the load on your pump. The increased load will draw more power anytime the pump is running, lead to premature wear, CFM losses, etc. I have never seen anyone factor in those long term costs when saying it's cheaper to run air.
Yes vertex discs can operate with .5 CFM per disc, but 1 CFM per disc is what was recommended to me. You are also starting with only 2 CFM so any losses and you will be less than 1 CFM per disc.
Last but not least, I can't tell you how many times I wished I had run electric instead of air simply for lights, etc, etc... With electric you have lots of options and possibilities, not so much with air.
