I have one in my 125g reef tank. Scruched up it's 6-7" long. When stretched out, it's at least 12". It just roots around the DSB. I have mushrooms, kenyas and zoas on the sand and it doesn't bother them at all. I found it when pulling the LR to catch my fish for QT. It creeped me out at first, but then I thought it was pretty cool.