Thanks for all the very helpful information. I am mulling over the options. It seems I could take all three of my current residents back to the pet store and start with a pair of pixies in my current tank. Two or three things argue against that: 1) I would hate to give up my pair of clowns. Mr. Tang is actually outgrowing the tank, so he probably needs to move out anyway, but the clowns are my babies. 2) I see that the the pixies are not recommended for seahorse newbs, a role for which I am eminently qualified, and 3) I see that the pixies require live food, which sounds like more than I am up for. (Also, the website is currently reporting that you are sold out of the pixies.)
I could start up a separate tank, but am not sure about taking on a whole new tank. So, again, thanks for all the info.