Will you see your Corals perk up when you use them ? Probably not, but you will find that in the long run your Reef will do much better if you do use them.
Micro-Algae Control : a product similar to the one just mentioned above, to control the growth of all forms of micro-algae, including slime, hair, and others, on rocks, glass, and in the aquarium.
Wilkens (1973) and Thiel (1989) both suggest the addition of "kalkwasser" or limewater, over and above the use of carbonate and bicarbonate additives.
Carbonate hardness is also a factor of how many algae, both micro and macro, are growing in the tank.
Even without biogenic decalcification, carbonate hardness is reduced and needs to be adjusted by the addition of an additive.