Joey.
From some notes I have in my notebook (but I don't recall the thread I gleaned them from.) Ted/Cary or Sue please correct these figures if they are wrong.
0.16 psi loss / 100' of 1/2" tubing
1 psi / 27" of water depth
I started out with the same compressor in one of my ponds. Fifty feet of 1/2" tubing hooked to one 9" diffuser (0.5mm slits) in 8' of water. Produced a nice boil. Use to run it from 10 p.m to 6 a.m.. At $0.07/kWh cost was about $4.00/month.
This summer I found a surplus store and picked up a GAST compressor, 2.6 cfm(@10psi) 2.4 amps for $34. With handling/shipping $52. Using seperate 1/2" lines (50' each in length) it easily handles two 9" disc diffusers, one is in 8' of water, the other is in 11'. According to the gauge at the compressor I'm running at 5-6 psi. Runtime has been cut to two 2hr periods at night. Cost/month is a little over $4. For the little pond two diffusers is overkill but I'm happy with the 9.0 mg/l D.O. reading I got from a surface water sample taken last month.
