I have three 2.5 gallon jugs for supplementation and I was hoping I would only have to mix new batches every 1-2 months but so far it's looking like I will have to mix new batches every 2-3 weeks. My reef is really sucking up a lot of CA, ALK and Mg.
I switch over to drews dosing pump myself from a reactor for a 150g SPs tank using 3g jugs and was mixing new batches about ever 3 weeks also, so I just doubled my mix per gallon, I now use 4 cups per gallon vs 2 cup and it's working out just great. I can now go just about 2 months before having to mix a new batch.
Mark