I have read people put a fine mesh like screen over them but I have an open back and they have not tried to escape I guess since they are fed well they have no reason to escape. I also keep the water a litlle below the rim so maybe that is a way to escape proof do know but after a month no...
Not reef safe with fish but would not bother coral and they are atlantic dwarf octos that get a little bigger than golf ball size and eat cut squid hermit crab and very fond of snails the most!
I have a couple of octopus for sale or trade they are about the size of a golf ball and eat really well if interested e-mail me at fishtank765@sbcglobal.net and i will get some pics for you. Thanks