Hello; Since many, if not most, suggest dosing for the total volume of a tank when using water conditioners I was working with the total volume of the tanks. I was not precisely thinking of a 100% WC.Correct me if I’m wrong but 500 gallons divided by 4 weeks would equal a 125 gallon water change weekly and the example you gave said you had 125 gallons. Did you perhaps mean to say you had a total of 250 gallons?
I get your question and think it is a good one. Another wrinkle in this SAFE vs. PRIME question.
Let me repeat that when I brought this up a few years ago that I was warned off from pre-mixing the SAFE for later use. So that is why Duane's recent post seemed of interest. As of now using SAFE dry seems the way to do it. I look forward to Duanes potential future post if he does in fact add more. I do not have the personal knowledge nor the personal experience to have a viable opinion.