I'm not certain that is an aiptasia. The clear tentacles look closes to a corrynactis anemone (or ball anemone). These come in all sorts of colors but the tentacles are almost always clear and have a "glitter" to them. If there are blass on the tips of each tentacle it is a ball anemone.
http://www.google.com/imgres?imgurl=http://www.underwater-photos.com/anemone3.jpg&imgrefurl=http://www.underwater-photos.com/pw035.html&h=432&w=648&sz=60&tbnid=xq9OI38F5s4QRM:&tbnh=90&tbnw=135&prev=/search%3Fq%3Dcorynactis%2Banemones%26tbm%3Disch%26tbo%3Du&zoom=1&q=corynactis+anemones&usg=__-8qxjpZDC0zSHeKXYE1ooXndiWI=&docid=_NdqYVK33TwYPM&hl=en&sa=X&ei=UahpUIG2FcTj0QG8voDwCw&ved=0CCgQ9QEwAQ&dur=4406
http://www.google.com/imgres?imgurl=http://www.underwater-photos.com/anemone3.jpg&imgrefurl=http://www.underwater-photos.com/pw035.html&h=432&w=648&sz=60&tbnid=xq9OI38F5s4QRM:&tbnh=90&tbnw=135&prev=/search%3Fq%3Dcorynactis%2Banemones%26tbm%3Disch%26tbo%3Du&zoom=1&q=corynactis+anemones&usg=__-8qxjpZDC0zSHeKXYE1ooXndiWI=&docid=_NdqYVK33TwYPM&hl=en&sa=X&ei=UahpUIG2FcTj0QG8voDwCw&ved=0CCgQ9QEwAQ&dur=4406