I suspect I am having nitrate problems because I overfeed, particularly flake foods. Most of my LR has been in there for 10 years, so there may be some old tank syndrome.
I have 8 fish in the 180g. I have a 55g sump with an AquaC 240 skimmer.
I do water changes religiously every week. I *thought* I was doing 20 gallon water changes every week, but it turns out they were closer to 10. Feeding heavily and doing 10 gallon water changes each week just doesn't get it done. I noticed the nitrate problem about 2 weeks ago. Since then, I have done five 30 gallon water changes. It is coming down, but not very fast (as you all know, nothing good ever happens fast in this hobby). I have also stopped feeding flake food since I noticed the problem, too.
It would be really nice if I could just fill up a 40 or 50 gallon container with RO/DI, roll it over to the tank, and do it that way. Thanks for your help, folks.