I figure just about every planted tank owner has airpumps that they've retired when they went to CO2.
My prototype doesn't have the second tank to stabilize the fluid level, and I'm not sure I'll bother to put it in considering it's already installed on the tank. I do have some 1mm diameter teflon tubing (for insulating wire) I'll try that first on prototype #2. It may choke off the airflow too much to be able to push the fluid up the tube - most of it goes in one whoosh, but the last quarter ml or so is left as dropplets in the tube that air can get around. If you care enough about precision to want the 1mm tubing, you'd probably want to be sure those droplets are blown out.