You do not need purple up it is just another overpriced product that is marketed to new hobbyists.
I dose kalkwasser in my 75gal tank and have coraline algae growing on everything. I do not add anything else. I have it automated with a liter meter dosing pump and spend less than 10 minutes per week maintaining calc and alk.
If you want a two part solution, again do not pay for the overpriced products at the pet store.
go to two part solution, or bulk reef supply. These guys sell the bulk material you can use to dose calcium and alk for a fraction of the cost.
Save your money!!
email me if you want more input.