I have never seen a negative comment on the product other than just personal preference. Seems like nobody has had a bad experience with it. After a quick look on forums, I see there are many different opinions about the Purple Up.
My personal opinion is that there is no reason for this product. I would think an alk. and calcium test kit would be money better spent. For me, it’s just an expensive Calcium additive with some magnesium an iodine kicker. If you test for Ca and alk and both are within normal limits, why would you need to add anymore using Purple Up?
Finally, coraline looks nice but it’s such a pain down the line.
You may use it if you want to spend the money but if your water params are where they should be there is no use for it.