I agree with ThatVietGuy on this. Others run their setup using Pre-Mix coolants and dyes just fine though. I have heard bad things about Hydrx, just look on some Google searches. It seems to clog up waterblocks for some people. However, to answer your question... If your using the HydrX PM, that's all you put into the loop as it's already premixed. You would simply buy a few bottles and pour in as much as needed. If your getting the standard HydrX and mixing yourself. It's specified right on the link you provided(1 Bottle per 16/oz of water for 3 yr protection, or 1 Bottle per 32/oz water for 1 yr protection). Also, a Silver Coil IS the biocide if that's what your asking. If your going to stick with HydrX, it shouldn't need any extra "ingredients" as they're in the HydrX solution itself.