Nutrient levels aren’t a “plug-and-play” type of thing where inputting someone’s “perfect” numbers will yield the same results on all tanks. The reason why we see such elevated numbers on awesome “master” tanks is due to their rate of uptake and maturity. I guarantee, those same tanks started out at MUCH lower nutrient levels and only increased them over time out of necessity. In most cases, a first-year tank really shouldn’t run over 5ppm nitrates and .06ppm phosphates. I can tell in the pic, simply by looking at the rock in the background that your N&P are too high for where your tank is right now. Your rocks should never look “fuzzy”. Been there, done that and my sps didn’t thrive until I started seeing red and purple spots on my rocks (coralline thrives in sps-ready parameters). As for RTN, there are instances where a whole frag is wiped out in a day. Typically this is from a major alk, ph or temp swing. There are also instances where blotches of tissue gradually fall off of the skeleton. Nitrates and phosphates that are too high for the system can have a stunting effect on coral and weaken them to the point of RTN. If it was STN or base recession, I’d say it was due to a lack of phosphates or more specifically, coral nutrition. What i’m noticing on your corals is a lack of polyps in those areas. Even on shaded portions of a birdsnest, you’ll still see polyp extension even if the coral looks ghost-white.
