well most clown fish do that. Dont ask me why but i would put an anemone in their to see if it will host in it and he wont do that any more. Mine stoped doing that when i put my first bubble tip in there.
I have 4 T5's over a 75 gallon tank with (besides other stuff) 3 cinni clowns hosting 3 long tentacle anemoenies (spelling?). all are doing fine. EXCEPT... they still do that tail shaking thing in the sand. messy...messy...messy!
You could try frog spawn or hammer/anchor.