well as with any reactor type things, there's no point getting one if your water tests out fine. IMO stuff like that is more for making the tank as much "hands off" as possible, so as to let it run itself. I personally dont run one and i've had my reef going with lots of corals (mostly softies tho, which dont use much of anything) for a long time...I have no reactors of any sort. I actually dont even run a skimmer on my 40, but i wish i did have one that i could run.
Keeping up with water changes will replace most of what is taken out, making other reactors and stuff "less" important in most cases (now i'm not sure how it is for SPS dominated tanks as far as how fast everything is used up cuz i've never had a tank like that)
