Uel, I saw a program on the learning channel I believe it was about public aquariums somewhat recently and there was soething in there about the keeping of octupi. Public aquariums put get this, ASTROTURF around the top of the tanks. Oddly enough, its the only solid thing that octupi absolutely cannot get a grip on. Looks pretty weird, but the public neverr really saw the tops of the tanks. I'm not too sure if it would be feasible in a home aquarium, but who knows?