I have several tanks. This guy is the size of a pen cap. I can't seem to find it. I was actually going to take it out and take it to someone that is in the hobby just because of octopuses but I can't find it. The tank is sealed very well. Not saying that this guy can't get out but it would be extremely difficult. I am going to keep the look out because I know they can squeeze through tiny cracks. He hiked onto a rock so I am sure he is in there somewhere. And for the clown, he ended up not eating and died. Which I hate to lose a fish but I was okay with that because he was sick when I brought him home. I will keep everyone updated. I have my Nikon D40 sitting next to the tank just incase I put and eye on him. I will see if I can get a picture to come out.