Dusty is CO-rect on the calcium reactor.You dont need that on a FOWLR tank.But a phosphate reactor is another story.You want to limit phosphates as much as possible,since its one of the main food sources of algae.
No need for a calcium reactor unless you have a reef tank heavy in SPS corals. Phosphate reactors are cheap (around $40) and are useful on any tank. There is no downside to having a phosphate reactor.
It's not a cure all, but it will lower phosphates to undectable levels. To rid yourself of nusiance algae you must also keep you nitrates down (20 is OK for FOWLR), use RO/DI water for top offs and water changes, use a quality skimmer and don't overfeed.