Antifreeze doesn't cool anything. It's only for anti-corrosive properties or the sub zero liquid cooler folks. tests have been run and antifreeze in even a 10% solution is worse temps than distilled water.
You have nothing in your loop that is a dissimilar metal issue, so you don't need it.
Distilled water, a few drops of Petras PHN nuke or an ianh Silver KillCoil. Thats it.