I’m trying to determine the possible root cause of my coolant changing from clear to a dark blue color and showing light greenish particles.

My main worry is that the build is freshly assembled (more on that later) and I’d have assumed that any algae growth / corrosion etc. would take some time.

Components include:

• full/pure copper radiators
• nickel and chrome plated cooling blocks and fittings (i.e. no aluminium, specifically)
• silicate glass reservoir
• PVC soft tubing
• Coolant: Aquatuning AT-Protect Clear (pre-mixed / undiluted)

All components were bought new and were left unused in the original packaging for about a year. Then, now that I’ve assembled the build, I’ve rinsed the radiators with distilled water (which was also a bit old, but showed no visible degradation/particles and an old, used Eheim pump. While rinsing for a few hours, no particles/residue was seen in the reservoir. I then removed the distilled water and filled the assembled system with the coolant mix a few hours later. After removing the air pockets and having the loop run for about half a day, the system was shutdown for the night.

The next day, I noticed the depicted degradations: the coolant liquid adopted a blue color (according to the label, it is not the UV reactive kind) visible under various lighting conditions including natural light, also there’s now resudue/particles visible in the reservoir and other parts of the loop.

I’m mainly wondering if the best course of action would be to just re-rinse and re-fill (with the same coolant - I’ve got enough left in the original bottle) or if I’ve missed some possible chemical reaction that would then just repeat.

Would the particles possibly be algae, copper oxyde or corroded PVC from the tubing? Is the blue coloring specifically a possible reaction to copper, some biological effect or does it hint at another specific reaction taking place?

Would algae have formed / copper corroded in the original packaging and then bloomed/grown this quickly (components were never exposed to water before assembly)? In that case, shouldn’t the initial 1-2 hours of rinsing with distilled water have exposed something?