Simple question. Should you dose the volume of your whole tank during a water change with prime or dose for just the amount of new water you're putting in if you're doing water changes straight from your tap to the tank. I've heard a few mixed reviews. I do a lot of water changes and have been dosing for the entire volume of my tank every time which sucks since they're a 125 gallon and a 90 gallon growout tanks that get several water changes per week so this prime bill is adding up.