A friend of mine tested my water with a d&d merck test. It showed I was at the limit on phosphate, Any higher would be bad for corals. My salifert kit has always come out 0000. D&D makes the rowa and the only test kit that I have witnessed to actually work at low levels. He uses the rowa and his tank looks like the great barrier reef while I have never used a phosphate binder and my tank looks like poo. I had trouble locating a d&d merk test so I ordered a hanna photometer to monitor the effectiveness of the rowa. For now I will use the rowa because I KNOW it works. Later I may try something less pricey and stay with it so long as it proves to be as effective as the rowa.