Very sad to announce I found my octopus dead under the couch this morning. I have a custom tight-fitting lid with very little squeezing space, but I was not weighing the lid down with anything heavy. I'm not 100% sure how he got out but think he must have lifted the lid just enough to squeeze through.
Very sad indeed as he was doing great! Eating shrimp off the line and live shore crabs, he had grown two or three times the size of when I got him. He still spent all his time denning but more and more time out at the opening to the den each evening, watching the world go by.
We will grieve for a bit before trying again, but I do think we will try this again as the whole family loved it. And would love to hear of some lid suggestions to octo-proof it. If I got some velcro strips to velcro/DualLock the lid to the tank would that do it? Also, I guess it would not look very elegant but could possible bungy the lid down...or maybe go with another lid design completely?