What type of carpet is it ? Can you post a pic ?
Depending on the carpet, they can easily reach a couple of feet in a tank !
You did'nt mention what type of lighting you have. Most anemones need strong lighting.
I had a merten's carpet and they truly are beautiful creatures. You can feed them silversides or small chunks of raw shrimp a couple times a week.
Becareful with that anemone b/c they will eat small fish !