If it is a bubble tip anemone (bta) then it is normal for it to deflate. Some deflate once every two days and some deflate every day. If your bta is new it will probably do it every day untill it is use to your tank. Are you feeding it regularly? They need meaty foods like raw shrimp, krill, or silversides. At the very least feed it once a week or once every three days. If your anemone is in a weak condition..like it won't grab the food.. then feed it every other day until it starts to take the food to its mouth on its own.