Because my fish room has close to 1,000g of water I was not doing my SW changes.
I was doing close to 700g of FW a week instead.
My Sw tank corals looked good for a long time, but in the end my SPS would brown out and my zoa/palys were faded. My LPS and Soft corals were thriving as they like the water a little richer in nutrients.
My system is a little less than 280g total volume and has a MRC-6 skimmer with ozone, I use zeo-lite products(bulk zeolites), I use Carbon and GFO, and all media is rinsed every 3 days and then replaced monthly(30 days). The intense chemical filtration and mechanical filtration has stopped things like Hair Algae and cyano, but PO4 is high as I feed a lot of dry foods.
After 2 years with only 2 large(300g) water changes, I have lost many SPS while others seem to do OK(not well). So now I have returned to my old ways and have been changing approx. 45g a week now. My LPS is looking fantastic! No change in SPS.
Part of the SPS problem is Alkalinity always dropping. That is why I am shopping for a CA reactor. I had a geo but the top cracked where it meets the tube.
There is no doubt that the water changes are helping my system but it will take at least 3 months to really see the positive affects.