Most coolants from various companies have biocides, you can add a silver coil as it don't cost a huge amount extra.

Personally i use deionized water and normal car anti freeze which has done me well over several years causing no build up of algae or corrosion in dissimilar metaks

I filled up my loop, which contains a 5 1/4" Koolance Drive Bay Reservoir, a CPU water block, two full cover GPU water blocks, >4 meter of 13/10 tubing, a 360 Aquaduct and a 9x140 Mo-Ra 3 Radiator with only one bottle of clear Double Protect Ultra and distilled water only. The loop is running over 2 years now without replacing the coolant. I just filled up the evaporated water with new distilled water again and again and nothing else and have no problems with algae till today. The coolant is as clear as 2 years ago. But I must say, that I never flushed the loop and components with tap water, because piped water contains a small amount of algae which remain in the water cooling loop after rinsing. The algae multiplies after time in the warm cooling water without water additives. You must consider though, the abstain of using tap water for flushing the loop could be the main reason why my coolant is almost as new as two years ago. Nevertheless, it also could be the effect of the Double Protect Ultra, even after diluting it this much.

Hi Neoload,

How long has your loop been running for? At first glance it does not look like algae to me, but more like the flux residue from the radiators. Did you flush them properly before assembling the loop?

I've been running my latest loop with just pure distilled water and a silver coil for 6 months now and no problems so far.

Kind regards,
Boris.