I bought a kit that came with whatever blue coolant, works just fine. Watercooling a 5870 and 5830 with it with a dual 120mm radiator, keeps them about 40 or so, depending on my ambient heat. I used 1/2" OD 3/8" ID primoflex tubing with the regular fittings, no compression.
I used a kill coil. Way less fuss than having to worry about oil or drops of whatever. Just stick it in the reservoir and call it a day.
Those coils are only for preventing biological growth, like algae, in the loop. It doesn't prevent corrosion. If you don't have differing metals in your loop, you shouldn't have to worry too much about corrosion.
I only have a tiny bit of ethylene gycol in my loop to lower viscosity of the water. (Helps purge out air bubbles.)
