I have noticed with two of my octopuses Leggs, O.briareus, and Pen, unknown species, Both perch on top of the live rock and appear to be sleeping. You can clearly see that their eyes are closed; however, if I make a sudden movement or approach the tank it is clear they can see me. I just watched Pen do it two seconds ago. He was sitting just outside his den with his eyes closed and I leaned back in my chair and stretched which caused him to quickly change camouflage and he opened his eyes. He briefly responded to my movements and now he appears to be sleeping again. So can they see through their eye lids? Or are their eyes not really closed?