If you are looking to get an anemone make sure your tank is mature. I would have to say wait at least 6 months. I have much experience with the trial and error of keeping them. The best anemone to get for a
maroon clown is an BTA. They are also among the hardiest anemones you could get. I have a maroon clown and he enjoys the BTA. He has hosted in a green bubble tip and a
rose bubble tip after the green one was lost to an intake. Please be careful when purchasing one, they are very sensitive to little changes and need great water quality.
Good luck and have fun,
Brian