I had seen some smaller ones in my tank, and I knew what it was, so I wasn't really worried. But when it started coming out of the rock, and coming, and coming, I was like, WOW, how big is that thing. It had roughly 5" outside of the rock, I don't know big it is, but surely it can't be much bigger than that. I was just more suprised that I hadn't seen him before last night.