I use it ad have good results. It is expensive for larger tanks though. Det out of whack. Drsfostersmith had the best price. I am switching to BRS 2 part to see howthat does.
I would reccomend making sure your alk and PH are in a stable ratio before starting purple up, otherwise you may see your PH and Kh get further out of whack. I used some DT's Ca anf Alk to stabalize the ratio (a 2 part), and then using the purple up has been good.