The Black Diamond blasting sand doesn't have a high or any CEC (cationic exchange capacity). From what I know about floramax I can't comment too much on it, but the flourite has high CEC and will over time absorb fertz from the water column (by my understanding). Either case root tabs will...
I have copper pipes and haven't run into issue with it yet (knock on wood) however I do run the water (cold) then fill up my buckets (I let them age). But one of the things at my work we have is a DI water system, check if you the chemistry dept has that that way you can fill up several 5...