Seem to recall reading a post that one way to tell the difference between aiptasia and a feather duster is that the feather duster retracts in its tube is this correct?
Aips are anemones and will accept food, curl up at night or if you touch it, will sting anything near it. Feather duster are worms with a tube they build, they cannot sting anything or eat meaty foods and will also retract (if healthy, dying ones won't).