I looked at your tank and I dont see any clean up crew.
I had high nitrates as well. And I needed to change the types of cleanup.
Adding a 2 Dimond Goby's and hermit crabs and other things that ster the sand. I also had to do 2 large water changes but the big issue was finding why it was going...
I purchased upgraded LED lighting and pumps. I dropped over 1000 in the system. About 4 months ago.
My system is 72" dual led lights with the bluetooth controller. It's from USA current it included DC 2 wave pumps, and 2 DC high flow filter pumps.
My corals and anemones seem to still be happy. I...