Randy I believe I have a problem, I discovered my nitrates to be very high between 25- 50ppm (most recently being the higher number) after moving my tank last August and have seemed to have issues with certain corals ever since moving this tank. I followed your advice and started vinegar dosing on my approx. 220g total volume system but I saw no nitrate reduction after nearly 2 months of dosing, so I stopped thinking that I was doing more harm than good . I had random stn on some sps during vinegar dosing and have lost some lps (long after I had already discontinued vinegar) to what I believe was a calcium overdose. After some deliberation since my nitrates were still around 50ppm I decided to start nopox dosing on 1/19 this year, I still have noticed no change in nitrates even after ramping up to the recommended 3ml per 100 liter dose. I also use a 29gallon separate fuge to grow chaeto and gracilaria, the chaeto has never really done much and the gracilaria seems to go through slow growth spurts here and there. I do seem to have some dinos that like to come and go on my frag rack as well, but other than that I have very little algae growth on the glass. Most of my corals seem to grow slow and my sps go through periods where they don't look good and even have sporadic stn on some spots of them since starting nopox, most of my montipora species have all gone pale grey with their polyps intact even before nopox. I've never really paid much attention to phosphate, maybe only testing a few times a year on previous tanks since I've always had good luck growing macroalgae as a nutrient export. But after testing with multiple brands of kits I have tonight I could not get a phosphate reading. Could all these issues i'm having come down to being phosphate deficient? Would you recommend dosing a source of phosphate to see if things improve?