Hard to say what the personality of yours might be. I've personally seen them get huge. And they aren't shy at all. I've never witnessed one attacking a tank mate, but I've heard plenty of stories. Always second hand information, never from one who saw it.
Still, IME with brittles and serpent stars, I've NEVER seen one that bold and move so fast out in the open. That and how big I've seen them made me return him to the lfs
. Replaced him with a greyish brittle who was very mild mannered. Would stay on a rock for days at a time. Had another red serpent at the same time. Both would feed from my hands. My red is currently in the SW
photo contest thread.