Update:
So I have not documented this on my system, since I have been sort of tracking an ongoing issue with this tank, and I have never experienced this before, so let me begin. I use a salt that mixes at 6.8dkh, and have been doing larger water changes each week at 25%, however, I would see alk increase in my tank on a daily basis of about .4dkh, which baffled me as I do not dose any minerals or trace. I decided to pull all the painted rock from the tank, most of it Real Reef Rock. I moved this rock into a separate tank I had laying around, now the tank is stable. In fairness, I had one more smaller piece of decorative rock that stayed in the system, and I was still climbing daily, but only at about.1-.2dkh. I removed it, and now only have real live rock from Fiji(air rock), and since removing all man made rock, I have now watched my alk stabilize. I am certain that this has caused me to lose about 6-8 corals since beginning this tank, and I am now seeing corals that looked washed out, burnt tips, and other signs of STN now coming back, showing polyps and gaining color. The single piece of live rock is around 20lbs, so not much natural filtration. I may add small pieces with corals mounted around the structure in time, but right now it looks pretty cool and simple, lol..
Part 2 of my update is tracking how NO3 and PO4 would work in my small system, especially due to it being limited for filtration area, as it is an AIO tank, and limited live rock. I was running about 5-10ppm on NO3 and 0.04 on PO4, depending on which day I tested, as the nutrients would creep until water change day, then go back down a bit. I have been using the Life Bio Fil passive in a mesh bag in the back of the filtration area. I had a BRS reactor lying around, I found a spot on the wall behind the tank, so it is hidden, and installed. I suspect about 150gph running through the media. From the time I installed it this way, I ran a NO3 and PO4 test 3 days later, without any water changes, and poof, NO3 no color change salifert, ZERO... PO4 also 0.00, so now I am using some of the AF supplements, as I need to get food to the corals. I am now feeding 2 times a day frozen, I only have 4 fish, but they are pigs. I cannot believe that running active with bio media versus passive would make this big of a difference. I am adding Bio S and Pro Bio S a couple of times per week, and NP Pro at a drop every few days. There is no real need for Phosphate remover at this point, and dosing. I suspect that if I dial down the flow rate through the media reactor, I might be able to control nutrients this way. Just thought I would share this experience. I am quite surprised to have ULNS in a AIO style tank as the skimmer is not over rated by any means.
Now the style of my system is a single low lying bommie, it looks pretty cool, I will have to upload a pic or 2 soon. The corals are looking better by the day, and the hopes for a minimalist display are in the works