I might be wrong, but I think that the blue ring octopus doesn't have venom. It has a symbiotic relationship with a bacteria that lives in it's mouth. It's just something I was told a little while ago, and I trust the source. It just another thing that makes you go hmmm :thinking: .
About octopi, they have no bones, so they aren't limited to what they can squeeze through. The only thing that does limit them is their beak. They also can lift up to twenty pounds, so make sure everything is secure on top. Octopi also have a naturally short life span, around 18 months. Very cool animals.