12' deep with tubing runs as long 500' at at your altitude (Saskatchewan averages around 2000' above sea level)a compressor would be running around 8.7 PSI. A Gast 1 HP vane compressor would give you about 10 CFM, but it would be running pretty close to its maximum PSI of around 10. If there is any back pressure from diffusers the PSI would go up causing more frequent need for maintenance on the compressor. If you need to go further into your lake than 500' you should consider piston compressors. Most aeration manufacturers have switched from vane compressors to piston compressors. Pistons can operate at higher PSI, require less maintenance and have less problems. You should have a professional size your lake and make a recomendation/design and then take it from there as to how you want to proceed on your budget.
