That's about as big as they get, and being reef safe is a contraversial discussion. There are hundreds, if not thousands of species that all look very similar, and although most are considered reef safe, I have personally seen them eat corals on occasion. The reason I say it is contraversial is because many people will still argue that they don't eat coral even though myself and others have witnessed it. They are known for eating things that are sick, injured or dying, so people can have the misconception that they are eating a coral even though it is just cleaning up afterward. However, I have seen zoanthid polyps perfectly happy and healthy only to be devoured by asterina stars right before my eyes. I still have thousands of them in my tank. I usually remove the biggest ones, but I wouldn't worry about them too much unless you notice them being a problem. If you have one, you surly have more. If you need to get rid of them, pick up a pair of Harlequin shrimp.