I have the Alita AL-80 running on my pond. Great little unit, and very quiet. It's a small diaphragm air pump, and pushes about 3 cfm. I only use 50' on air line and I get a real good air stream through a 12" EPDM diffuser. It runs on 90 watts.
Running a shop air compressor that is made for moderate duty cycles, high pressure, and relatively low volume at 7 watts at 220V will use about 1540 watts. Running it through an air regulator maintains backpressure against the pump and probably delivers only slightly more air volume to the diffuser. Putting this on a timer limits the amount of air being transferred to the pond, and starting and stopping the compressor again is inefficient, and wears on the compressor. And, they are noisy.
I realize that a lot of the new shop compressors are oil less, and will last a long time, but think about this mass of equipment being used to put a small stream of air into a pond.
On another application, we have a turbine air compressor that supports five stone type diffuser heads on a 15 acre lake that is made for the purpose. Some of the runs are over a thousand feet. Efficient, quiet, and a continuous duty cycle compressors are a joy. Yes they cost a little money, but I would think this is a long term proposition and will save money and energy in the long run.
My 2 cents.
