Don't get a carpet anemone if you want to keep just about anything else alive in your tank. There was a recent article about them in one of my fish magazines, though I can't remember at this point which magazine it was. Let me paraphrase what I read:
By and large, carpet 'nems get HUGE, need VERY specific tank and lighting conditions, have a VERY potent sting, and are VERY sticky and aggressive. You could keep anemone shrimp, clownfish, and possibly damsels in a tank with a carpet 'nem, but just about any other livestock could turn into anemone food if it got too close.
