I gave up on the colored fluids a long time ago. Maybe the situation has improved, but when I was doing it some years ago, there was always a lot of residue after a while in the loop. And I tried all the reputable manufacturers. Consequently, the flow would come down as well.
Distilled water, a silver coil and a few drops of biocide and my loop has been maintenance free for years with the same flow as in the beginning.