Update:
I think there are several things that were going on all at the same time. First...I did start heavy water changes....40g per week (of 200g twv) and I added Matrix through a canister filter. That dropped nitrates a little but not as much as I'd hoped.
I noticed in one corner of the tank at the bottom of an overflow was something black in color just laying on the sandbed. I vacuumed it out and it was BLACK and stunk! I cleaned every where....sump, skimmer, sandbed in the tank....did about 50g of vacuuming and that brought nitrates down to the 15-20 range. Still not where I wanted to be. I think what I have is "old tank syndrome". Almost all of my sand came from a prior tank so that makes it all in the 6 - 7 year old range. I continue to vacuum that one corner on a weekly basis and while it's not as dark now as it once was, I still get a collection of detrius there. Seems odd to me but there it is.
Finally, I realized that I had removed about 40 lbs of live rock when I got rid of a lot of softies (I let the rock go with the corals) but I didn't replace any of it. In effect, I reduced the anaerobic bacteria available. I've since increased the live rock by around 30-40 lbs plus I added about 15 lbs of rubble to what was my refugium and I can already see an improvement.
I'm still doing weekly water changes but have backed those down to 20g one week alternating with 10g the following week. That amounts to 60g per month. I'm also planning to put vodka dosing in. The doser is set up and I have the bottle of vodka, now just looking at the formula to determine how much on a daily basis.
