Running Zeo seems like another big headache and i'm not sure i'm advanced enough to deal with it.
I am going to keep my Alk steady at 8.5 and keep siphoning out as much detritus as I possible can. Again, my biggest issue is that I don't see anything on the rock to blow off. When I use a turkey baster I see nothing coming off the rocks.
I've read through this entire thread. Much of what you're doing is the right initial things - stop dosing mystery products, remove the bio pellets, and get control of your minor element concentrations (alk, Ca & Mg).
One of my thoughts is precisely the opposite of what the comments have been about your lights. I don't have the Hydra 52s, but did have 2 Vegas 14" off of the water on a tank 22" deep. Setting the Vegas for about 65% blue/royal blue/deep blue and about 55% white intensity was absolutely nuking the SPS that was about 1/2 up the water column. And the Vegas are a bit weaker fixture than you're using. It was enough to actually sun-burn a new clam acquisition that was placed on the sand (fortunately, I realized what was happening and the clam survived).
That said, I was running a bit longer light program than yours - my total photoperiod was about 15 hours, with the actual effective lighting part about 12 hours a day, and the intense period of light at about 5 hours.
Without a PAR meter, it's
really difficult to judge the intensity of LEDs. What I can tell you without doubt is that most SPS will survive absolutely fine at much, much lower intensities than one would expect. They don't grow all that much - higher intensities are required for that - but they don't die, either. If you want to experiment, you can move a couple of frags away from the "light islands" in your tank and see how they do.
Back to more important possibilities: Your nutrient concentrations, btw, are absolutely fine. The idea that a very slightly elevated phosphate and/or nitrate is causing your RTN problems is way, way off the mark. And there are tons and tons of examples in the SPS forum to back that up. So don't concern yourself with this.
It's absolutely unnecessary to vacuum your sandbed with every water change, or stir it up in any way shape, or form. You can do it if you want, but it's most certainly not necessary nor even all that beneficial. I've a 20 gallon nano with very rapidly growing SPS that has had the same 2" sandbed for the last 10 years. Very occasionally I may vacuum the sand within 2" of the front glass, but the rest of it remains undisturbed.
The one thing I haven't seen anyone bring up in this thread is water. While it's not true that you need to constantly obsess over 0 TDS water as long as you're running a proper RODI system, it's most definitely the case that you need to maintain it. When was the last time you changed your carbon (and what do you use), DI resin and RO membrane?
