Well I understand your reasoning for sure. But just to reiterate what everyone is saying kinda: The low amount of nuisance algae in a successful sps tank is due to an efficient means of exporting excess nutrients from the water. Whether it be from heavy skimming, big water changes, few fish/feedings, gfo reactors, refugiums, or carbon dosing. A calcium reactor really has little or nothing to do with it.
A calcium reactor isn't used in all sps tanks. Many ppl use a kalk reactor, or dose liquid or powder supplements. Calcium reactors and the other methods mentioned are used to maintain Calcium, Alkalinity, and Magnesium at the proper levels as sps need supersaturated levels of calcium to build their skeletons and grow.
The connection between a sps tank with a calcium reactor makes sense. But you may not be looking "under the hood" entirely. I guarantee you there's a few more reactors or other methods mentioned above going on. And those things are the reason for the low algae growth. Exporting nutrients efficiently will limit algae growth.
Here's an article by Randy you might like reading
http://reefkeeping.com/issues/2006-09/rhf/index.php
The paragraph: Phosphate Reduction via Calcium Phosphate Precipitation, might be what your thinking about. But overall through the article you'll see that there are more efficient ways of controlling algae than others. Hope this helps bud!