I found some baby octopus' inside empty shells on a grass flat. you would not know anything was in the shell because they take a piece of seaweed or grass and cover the opening of the shell. i thought they would be cool to have in my tank, but i was wrong. i think they are nocturnal, i never saw it come out of hiding. with its legs stretched out it was about as big around as a golf ball, and i caught it escaping through the hole in the lid made for air tube. it wasn't worth keeping something that you never see and is impossible to keep in the tank, so i took them back and let em go.