There is no way to predict clown behavior. Even if you had an anemone they might not host in it...BUT in my experience they usually start. Mine use frogspawn, a goniopora (I dont recommend due to their difficulty), leathers, etc. I even have some fry that use caulerpa algae. For corals I'd say frogspawn, hammers, leathers...a torch might be good since it looks a lot like a anemone...but they will host about anything. As for a anemone getting too big for your tank...it depends on what all you want to keep. They do get big but would never get physically TOO big for that tank, just might get big enough to bother corals and such.
Angela