To share, I have been using the reef resh system for about 8 weeks now, and I unplugged rowaphos when I started. Prior to this, rowa can keep my PO4 at undetectable levels (Hanna checker), but I noticed that PO4 has crept up to 0.06ppm since then. Could be that my skimmer is not skimming as efficiently as I like, I don't know. Having said that, overall health of the corals seem to have improved since I started reef resh.
I reintroduced rowa last weekend and shockingly, my PO4 dropped back down to undetectable levels within a day. I don't like the sudden drop at all and now hoping that the drop is not going to cause any negative effects on my corals, especially the SPS corals.