Yeah I have 2 hosting my Xenia colony now and a 3rd hosting a toadstool. I realized mine will host about anything they can swim in. Seen them in my torch and frogspawn before.
The host would be the anemone or coral the clown resides in, while they would normally prefer their natural host be what they would be found in the wild, they do take to alternatives, mainly soft corals.
I have a mated pair of clowns in my sump....where I have a crop of hair algae that would make Fabio's hair look like a crew cut. I made an attempt to remove this about a month ago, and was brutally attacked by the clowns. So I continue to have a nice patch of hair algae that keeps my clowns happy.
One of my clowns was hosting a duncan and the other one nothing till I got a carpet anemone and the one hosting nothing won a battle over that and a few weeks later they decided they could share. Wouldn't it be nice if people could do the same