Aiptasia species, also known as Glass, Rock, Tube, or Glassrose anemones, can harm your reef in two ways: they can sting your more desirable sessile livestock and multiply rapidly to aggressively compete for food and space. In addition, they are notoriously difficult to eliminate. Because they are so tiny, they can quickly withdraw into tiny holes. In addition, if you try to siphon, pull, or cut one out and don't remove most of it, what is left can regenerate, sometimes into multiple anemones leaving you with more than you started with. Hope this helps..