I've had them host to all sorts of stuff from frog spawn, brains, hammers, torch, galaxia, xenia, mushrooms, to anemones. They typically cause whatever else they host with to die. May try moving the flowerpot to the sump or fuge for a day or two to confuse the clowns.

I once had a panther grouper host to a Gigas clam, the clam died after about 2 weeks of this.