Very nice animal.
The expansion and contraction are perfectly normal. Since an anemone's body is made up of mostly water, it contracts to expel both digested food and metabolic waste. It also brings in water to balance it's own internal chemestry. Some will go through this cycle of expansion/contraction more than others even in the same tank with the same feeding schedule. Remember to feed often with small foods, shrimp, mysis, krill, squid etc.. I feed mine once a day and they do very well.
Good Luck