Yes, I've been using Reef Roids. At the amount suggested by the manufacturer (which I've read is considered to be too much by some people), I was getting no increase in NO3 or PO4.Are you spot feeding your corals? If you’re feeding the zoas and other corals, then that will elevate your nutrients. I grow chaeto to keep my PO4 in check as I feed reef roids twice a week. Even with chaeto running in my fuge with 14 hour light cycle, my PO4 stays around 0.1 and my NO3 around 12. I have a mixed reef with sps, LPS and zoas.