While manufacturers of sealed loops may have low/no bateria in the loop from the factory, we can assume home made loops will be contaminated. Either way, it is a manageable thing. As far as nanometallic cooling, I looked into that. With a 2% copper particle infusion with water, the benefit is only 3.7-3.9% better cooling (MIT study on nanofluids). This was done with distilled water with a pH of 7.3. Now, with an oil based fluid it may be a bit better, but it is still limited to the thermal conductivity of the fluid. You also make the fluid more alkaline by adding metallic particles. Speaking of, I'm been hiking across the internets for the last week trying to find the TC of mineral oil... anyone know where I can find it!?! Specific Heat i've got, but doesn't help so much with the calculations. Can anyone recommend cheap compression fittings for copper? I like the look of BitsPower, but at $20/ea shipped, it hurts da wallet. I saw some permanent push-in style fittings, but they have a plastic sleeve that might disolve in mineral oil.