Long Term Water Storage

I bought a tank of 1,700 gallons of water storage that has been buried in my garden. I was told that I can use colloidal silver to preserve water, but I can not find information or to confirm that training on how to do it. How to save water in underground storage in the long term? How long will this last? Will I run the water or add other preservatives?

They have a lamp that is ultra-violent with a clear plastic tube that will kill everything. Even a simpler way is to carbonate the water.Nature it near some volcanoes. It does not taste good, but anything that will kill everything.