This is an emerging/growing part of the hobby. The only one I can think of off-hand is
Sustainable Aquatics. I have not bought from them personally, but I do admire their conviction, particularly in a fickle hobby.
There's just not enough fish available yet. I know there are a myriad of people trying to breed a variety of fish and inverts, but the success rate is meager at this point. A lot of work has been put into breeding cleaner shrimp, but as far as I know, no consistent success has been reported.
However, with your wife's leanings, there's no reason you can't set up a sweet reef with anemones and clownfish as a start. It could be nearly a "species" tank, but keep in mind that anemones require a lot of light to stay in one place, and in general are not coral friendly. I have them in my tank and it can be quite challenging to grow corals and anemones side-by-side.
My "parent" GBTA has grown to grotesque proportions and is taking up some serious real estate. So is my PLTA. But, I find the symbiotic relationships of the reef to be very interesting so I am more willing than most to handle the risk. Because I am using 1000W lamps, my anemones stay put, on the bottom, and it is extremely rare for one to move at all.
That is not the case in most reef systems so beware!
Good luck!
