I have three pairs, each in their own ten gal. with clay pots (which they seem to love). All are tied into my reef so water quality is not an issue. All seem to be doing quite well except, no eggs, yet... This has been set up for about 6 months. Clowns dont seem to travel much, specifically if they host something. I have a pair in my reef, and they are either hosting the kenya tree, or gsp. Two anemones in there too, go figure. Perhaps the addition of a host would make them more comfortable.
Just my 2c.