Brett, I bought 4 diffuser stones and a check valve as separate pieces (no kit) from Aquatic Ecosystems, they were about $4 each I think. This was about 7 years ago when the conventional wisdom was that air stones were better than diaphragm aerators. I understand the diaphragm ones are better now and perhaps that's the way I'd go if I did this again. They are more expensive but should theoretically last longer. Although my air stones have been in use for 7 years with no problems. I plumbed those up myself just using PVC fittings from the hardware store. I mounted them on top of an old plastic kitchen cutting board so that they wouldn't lay right on the bottom and stir up muck. Attached bricks to hold it down. I really don't know if the compressor you found at grainger would work. Not sure if it's meant for continuous duty. You would have to install a valve in line to control the flow so you don't get too much air and so it doesn't run all the time. Too much air through a diffuser is not a good thing. If I tried that pump I think I'd just install a ball valve in the line and adjust it until I get what looks to be the right amount of air from the aerator. Then you'd have to see how often the pump ran to keep up. I think most air compressors like this are only designed to run maybe 25% of the time. If it runs more than that it probably won't last long. That one is also going to be noisy. But, it might be worth a try since it would make a pretty inexpensive system. If it doesn't work you are only out $62. Aquatic Ecosystems also has some guidelines right on their web site to help figure out what sized pump you need. I think for a 1.5 acre pond you could get by with 1/4 HP. If you want a truly industrial pump that will last for years you want either a centrifugal pump, piston pump, or vane pump depending on how much pressure you need to provide (how long are your lines and how deep is your aerator?). Whatever you do if you like do-it-youself I would spend some time on the Aquatic Ecosystems site, they have tons of guidance and instructions on how to make all the decisiions. Then after you decide go on the internet and find the best price for what you need. I always try to by some stuff from them just to pay them back for the advice. A good industrial pump will cost you around $400.
