I once tried the Swiftech Hydrx in my loop for a couple months, and never had issue with it. I also tried yellow antifreeze a while before that (looked like urine, which is the effect I was going for). I also use silicone tubing, so it's milky white in color, but was easier to bend. I'll live with the potential seepage of it over time, and already plumbed in an extra reserve section for that reason.
Anyway, neither of those gave me problems, both are UV active (if that's your thing...not mine). However, I did not mix it quite at the full strength as suggested, but diluted somewhat. I also dropped in a kill coil, and had some PT Nuke nearby for an added bonus. I eventually rid myself of the motherboard, and put the CPU in a different (sig) machine. The water loop has been closed since, and sitting for a couple months. I check on it occasionally to see if anything is forming, and so far I've seen no deposits or clogging. It does stain lightly, but that doesn't bother me. I also cooked my blocks and radiators in distilled water after flushing them out, so whatever may have been in there is likely dead. So far so good. If it clogs, I'll be sure to post back and confirm.