IMO, these guys not only need space but also interaction. When you have a creature with 8 arms, and the brain capacity these guys do, how can you ever provide the correct environment?
They need to be stimulated, or they get bored. Kinda the same way parrots do.
I can see it now. Someone with a glass tank will buy it. Then when they come home to a busted tank and flooded house, they will wonder why.
Home Owner: "What happened"
Octo: "Well, I was bored"
Home Owner: "and...."
Octo: " I was playing catch with the tang. I threw the rock, and he could not catch it"
Home Owner: "What did we say about having fun?"
Octo: " I know. I know. I am not in the ocean anymore, and There are rules."
Home Owner: "That is right. Now clean up your mess"
Octo: "Cant the tang help, he is the one that missed the rock....stupid fish"
Home Owner: "Tell the tang you are sorry, and besides you have eight arms, the mess should be cleaned up very quickly"
Octo: "Doh."
Tang; "help!!! Help!!! I cant breath" Flop. Flop. Flop
~Michael