I can not advise to the benefits of injecting air into a water supply stream. I guess every little bit helps. I do not think that running air out your water supply line alone is going to be efficient at all. You really need a diffuser to maximize the air's effects on moving water.

What ever you do, do not use a standard air compressor that has oil in it. You'll get that rainbow sheen on your pond surface. A little oil contamination goes along way. I would recommend a rotary, diaphragm, or piston air pump (in that order of personal preference) to "inject' the air, BUT, at this point, spend a little more and add some diffusers and weighted air line and be done and done right (meaning efficiently and most effectively).

All things considered, if you are OK with marginal positive affects...the venturi is the cheapest way to go.

Fish on!,
Noel