I've used it in the past. Had alright results. I've used several products over the years to keep calcium and alkalinity high. Caribsea makes a good product. I use the arogomite right now, which is similar to purple up and have had amazing coralline growth. I also use reef builder with reef advantage calcium by seachem. The key is to keep alkalinity high and balanced with calcium. Test often, because when alkalinity drops, calcium is not able to be absorbed. I would think using an alkalinity supplement along with a calcium supplement then adding purple up as a supplement a couple times a week. Like I said, this is what works for me. I have a lot of demand with my system, so it takes alot of monitoring and adding different supplements. I've never had just one be enough. Although the arogomite does seem to be a good balanced supplement.
Richard