Rose Anemone - Normal behavior?

[Poisson]

I've had a Rose anemone for a week (4" diameter). Water is mature and pristine. During the day, it looks great (well-adhered, turgid and responsive to surroundings). Once lights turn off, the anemone slowly goes flacid, shrinks, rolls up (1 1/2" ball) and moves to a tight spot between some rocks. In the late morning, it moves back to its previous spot and perks up. This behavior started 2 days after I put it in the tank when it released a brown stringy excrement. A few days later, it "pooped" out a 1/4" ball of something. There's been no excrement, but still anemone shrinks every night and opens up every morning.

So, is this daily routine of shrinking and hiding, then perking up normal? Part of the excretion process? Is it sick?

The excretement is it pooping. As long as it keeps coming out I wouldn't worry.