Does anybody Know What This Is???

[HollyG]

That's a Majano Anemone. I've had them in my tank and they aren't nearly as difficult to get rid of at Aptasia! I finally decided to get rid of mine because it was getting a good size, but it didn't spread. They most definately can though! They hide during the day and come out at night to try and catch any food particles that go by in the water column. They can move just like any other true anemone, but I found that they only move if there is something seriously bothering/harming them. You can get rid of them easily with Aptasia X. Mine just took a single large dose to die. I would suggest getting rid of it thought since you do know where it is. You don't wan tto leave it for too long then it ends up moving and in such a big tank you may not find it again and suddenly see them popping up everywhere. Better safe than sorry good luck!