Art,
Both the Fox and Blue Bowl do an excellent job in really fine gold recovery but you will have to fiddle with either a bit. It will take some time to get down to 200 minus and it can be done. With both units first assure that you are classified to the smallest gold that you have. If I have a couple of pieces of gold that are + my sizing I will pick those out and continue to classify down. Let's say that I have some 100+ and some 200+ and 200- gold. I will run the 100+ separately then the 200+ and finally the 200- . This works for anything 20- as well, just pick your battles. From there I run each separately making the adjustments specific for the sizing. With the Fox, I always add a bit of magnetic sands at a mesh between 20 & 50 seems to work better for me. Do not forget to use a surfactant, Jet Dry works fine but there are others that are a lot better.
Hope this helps.

Kevin

Spiral Wheels do work, but I cannot get 100% fine, flour gold to just drop in the container without black sand, unless I am also losing gold. I typically classify, run to capture gold, black sand and garnets (My wife likes those). I then run to capture gold and less black sand. Then I hand pan down to close to pure gold. I am a beginner though, only been at it a couple years. I only use it when running larger batches of dredge concentrates.

It does take lots of adjustment with water flow, and bowl angle to learn to capture what you want. Lots of good youtube videos on spiral wheel and panning techniques for fine gold.