Cooling Water Additives / Dyes for Liquid Cooling Systems
Veteran Watercooling enthusiasts will tell you that all you need to use in your loop is distilled water. They would be right, but if you want coloured fluid then that is available too.
Dye in watercooling fluid does NOT clog up your blocks. It may stain them slightly over a long period of time but they can be cleaned.
Overclockers UK has an expansive range of coolants to suit all styles and requirements.
To add to your fluid, you can use some methods to stop micro-bacteria building up.
Adding a few drops of Biocide or a Silver Kill Coil into the reservoir of your loop should ensure that there is no build up of bacteria over time.