I have one also. Close to a foot across. While I think it is really interesting I wish I had never gotten it. My clowns seem to get into fights with other fish and lure them to their deaths. Now the 3 of them have a 65 gallon RedSea tank to themselves. I would love to get rid of the tank but I cannot give it away in good conscience. This has been like this for around 8 years. And no way could I put them into my large DT.
I am glad you love yours. I keep hoping mine dies! Sorry that is how I feel. I even named it hoping that would get it to die. Nope!