I probably lucked out on this system. I do not do much maintenance on it. I do a 45gallons water change every week and clean out the skimmer. Every month or so, I would change out the carbon and GFO. I use IO 200gallons box salt that comes with 4 bags of salt in the box that makes roughly 45gallons with SG of 1.025.
ALK/CA/MG is provided by the calcium reactor and the dosing units. I dose ALK and CA because my reactor is undersized and I don't want the PH to drop too much because of the excess of CO2. ALK is 8dKH, CA=420ppm, MG=1400ppm
Last time I tested PO4(sometime last year) is 0.04ppm. I generally try to keep is under 0.1ppm. If it rises above that, I would change out the GFO. I haven't tested nitrate for the longest time.
I don't do any sand bad stirring or cleaning. I have about 6 fighting conches in the tank that work pretty hard on the sand. My whitetail bristle tang also peck on the sand. I recently added a female mandarin and I've seen both mandarins going at it on the sand. Being able to sustain a mandarin without adding copepods is the biggest reward to me. I had the male for about 4 months now and it's getting huge with a very long dorsal fin spike. I constantly look at the belly to see if it has enough to eat and that it's not pinched. If it's pinched, the mandarin need added source of food(which can be quite painful). The male has been doing so good that I decided to add a female. It was difficult for me to obtain a female. All I've seen were males. I finally found one at Jays about two weeks ago but with a pinched stomach. I kept walking back and forth but decided to bring it home. The female is doing better but it still have a slight pinched belly but it's improving.
I also had Aquatic Creation held me a Biota female mandarin. When I got here and saw the mandarin, it was tiny(3/4") and I realized it probably will not work since my male is about 3.5". It either will get lost in the tank or the male might give it a little bite and that would be the end of it. It was beautiful though. I would have a pair of these if I didn't have such a big male already.