premixing

I have read that a few of us pre-mix Safe by mixing it with water in an empty 500ml Prime bottle. Can any of you who do this please tell me how much Safe to add to the bottle? Thanks!

Ok, all you water experts. My question is: If I leave for vacation for 4 weeks, can I premake bucktes of dechlorinated water for the fish sitter? I have a bunch of 2 gallon jugs with lids. Will the water get nasty over the course of, 1, 2 , 3 or 4 weeks? Is it safe to use after sitting around...