There certainly isn't a garentee that they would host one anemone over another. I do have a pair of false percs that are currently hosting a sebae and have been for years. But if I were to say move the tank tmr and put the rock and anemone in the exact same spot, there is a chance they would stop hosting iit. I've read about clowns hosting a nem, gets moved and stops hosting with the Nem. Then a year later for no reason decides its going to host with it again. At this point I'd wait. Actually what I would try would be to slightly rearrange some rock work. Especially if there is a spot the clowns like to hang out. Change up their routine and it wouldn't surprise me to see them hooking up with your nem.