[Gooserider]

If you have algae cells in your loop (or other micro organisms) you WILL get growth sooner or later. Keeping the system in the dark may slow it down, but won't stop it.

The optimum solution is to run a very clean, non contaminated system to start with, and then use a biocide on top of it.

A clean system is achieved by avoiding contamination in the first place, but also by using Airspirit's "*sol flush" or other biocidal cleansing before filling with distilled water and other ingredients from CLEAN containers, using CLEAN tools.

Do NOT use chlorine for a biocide, it is damaging to your metals, and isn't that effective. Non-chlorine/bromine hot tub and spa sanitizer is good, as are some of the other non-metal hostile biocides. Anti-freeze and water wetter type compounds are NOT particularly good biocides, indeed some critters will grow on them. (Engines don't have growth problems because of the heat they produce)

UV sanitizer lights are a mixed bag. They must be the right wavelength to work at all (hint, if you can look at it safely, it is the wrong wavelength. Case UV lights will not work as sanitizers!) If they do work, they will only work on the coolant that passes through them. They will do nothing to stop stuff that sticks to the walls of the plumbing.

Gooserider