I have never heard of this product (calcium block), it may work. Though I would rather add calcium regurlarly, I tend however to displace such products from my life. They tend to not work, most of the time.
I beleave that a calcium level of 400 mg/L, a carbanate hardness of atleast 8 dKH and a strodium level of around 9 mg/L are the ideal conditions for coraline algea growth as well of course with other stony corals.
Calcium reactors work great, they add alkalinity and calcium to a closed aquarium system. These systems are great for the aquariust that is tired of adding tedious applications of calcium to the tank. They ahve tremendious ph buffing capabilities, always is at 8.0 to 8.3. Which is something that is a constant struggle with many aquariusts.
Basically just saying if you want coraline algae to grow than reach the levels specified with additives. Or purchase a calcium reactor. I don't know of the calcium block, so I won't discredit the claim, I don't know.
Good Luck...