Honestly, I know several people that keep LPS and softie reef tanks and rarely do water changes. I have seen the tanks with my own eyes. One of them is the sickest seahorse and pipefish display I've ever seen. Complete with crazy aussie acans. the reef keeper prefers the nutrient rich environment and there is little issue with running lower Ca and Mag.
The other guy has a really nice in-wall 65 G. He used to test all the time and do waterchanges religiously and just kinda slacked off. He actually made it a year without a waterchange. He just let the corals kinda do their own natural selection. He has some HUGE beautiful orange yummas, beautiful euphillia species, and various other corals (it's been about 6 months since I've seen it).
Anyway, my point is, that thing may do nothing and the tank could pull thru. Can't help you with any actual product review, but IMO you might have just as good luck by rubbing peanut butter on the side panes of the tank's glass than you would using that thing.