[wooddood]

all kidding aside, i have had aptasia in the past and they were always brown in color. i have never seen one that was white like your pic but again i could be wrong. if it were me i would keep an eye on it and see if any more start to pop up around it. if so then it may be an aptasia. if it's not touching anything close to it leave it alone and see what it does. also i would do a search on aptasia and read all you can about them. like witt said there not killers but if left unattended will over run your tank. it's really not anything to worked up over just keep an eye on it and see if it multiplies. if it does then i would kill it. we have always used kalkwasser to kill them but you may have to do it a few times to kill it. thier tuff little boogers. i have also heard good things about joes juice but have never used it my self. do what you think you should it's your tank i'm just telling you what i would do. good luck and keep us posted. dave!