FWIW, Ron Shimek has said on many occasions that the sand bed in a nano lacks the size to support a solid nitrate-reducing bacteria population; there's just not enough room to creat anaerobic conditions. In my nano, soon to be for sale, I use a separate sump/refugium to grow caulerpa. It's a 5 1/2 gallon refugium for a 10 gal tank. Over the year and a half of this system's life, I've never had detectable nitrate using the hagen or sea test kits.

I'd keep changing water, set up a caulerpa growth refugium, and keep the fish load teeny-tiny, like 1 small fish only.

I'm going to try to post a few pics of my nano. It's a pretty cool set up; supports acro/monti growth really well, and my BTA has split once and is about to again.

Matt