The Red Sea product is a kalkwasser aka limewater product and meant for maintenance. It is not good for correcting improper chemistry.
Red Sea Reef Success Calk wrote:
Reef Success Calk is claimed to be a balanced supplement aimed to replenish calcium and carbonates in the right proportions at the same rate as they're removed by invertebrates. It's a maintenance supplement designed for regular daily or weekly use on water with an initial calcium level of 380 - 420ppm. The recommend technique for dosing Calk is to monitor the calcium and alkalinity levels daily for a week to monitor their decline and determine the approximate rate at which they are being utilised by the inverts and algae present.
It's dosed at a rate of around 0.5g per 100 l./22
gal., but you need to test the alkalinity regularly and make adjustments to the amount added depending on the results. No details on constituents or concentration are provided so we can't comment on how much it's likely to cost to use or how effective it is at maintaining balanced calcium and alkalinity levels.
As you can see by there own product statement, it is really only recommended for maintaining the levels....