Ah, and that's how you prevent microbial growth?
It amazes me that anything could grow in distilled water, but I guess the pipes & hoses aren't guaranteed to be perfectly clean.
Distilled water is pure H2O but the hoses, fittings and other components will have micro-nutrients on them from fingers, all it then takes is energy in the form of heat and some random bacteria can grow. Silver is a very strong anti-microbial agent that's not very toxic to us humans.
The antibacterial activity of silver has long been known and has found a variety of applications because its toxicity to human cells is considerably lower than to bacteria. The most widely documented uses are prophylactic treatment of burns ...
www.ncbi.nlm.nih.gov
There are two downsides to this, first is that it takes awhile for the silver molecules to build up in the water, it's not instant. Second is that free oxygen in the water can cause silver to form silver oxide, a blueish black coat that can build up whatever you have the silver at and it'll have to be cleaned every few years. You should be replacing the water and hoses every year or two anyway, so not a big deal. I handle this my scheduling my maintenance at the same time I do a platform upgrade, switching out the CPU / MB / GPU requires draining and rebuilding the loop, so good time to do cleaning / etc.