I agree with Spiderwoman, you need to allow your tank to mature before you start adding an anenome. You will also need to upgrade your lighting. Anenomes require strong lighting, and you would need a minimum of high output T-5s, and would most likely be better off spending the money on Metal Halide lighting.
If you really want to try to get your clowns to host and given the age of your setup, I believe that you can find decorative anenomes that look decent. This way you can have the look of it and none of the worries and stress of keeping an anenome, and your clowns might host it