Eeerrrr... I had a -huge- problem with uv dye.
I wanted all my tubes to glow red. And with dye bought from a cooling shop which will remain nameless, my tubes did glow - and looked the dogs danglies at that.
Until my passive radiator started to corrode. Its an Innovatek Passive, and it started leeching salts or something out of one of the rubber sealed joints. On advice from Innovatek, I had to flush the whole system several times, and found bits of rubber actually floating around in the system. Big f**k up.
Now I just use deionised water, and a swiched to orange coloured tubing. MUCH safer
and it still looks ok.