lol that's what thought.

why would the sump be such a bad idea?

Sump is bad as it would be difficult to completely seal it. An octopus can squeeze through any hole big enough to fit its beak through which is the only really hard part of its body. An octo tank has to be extremely well sealed as they are great escape artists.

There is something i must say even this is an older post. Is this octopus picture of "sphelps" that on this thread, this spieces of octopus is called "Macropus" and yes it is very nocturnal iv had one before and it was quite hard seeing it ever. So id go for a brown octopus or "vulgaris", Its quite easy to tell the differants between the vulgaris and macropus. Macropuses there eyes are bigger and there skin color is mostly red with green dots, and there two front arms are longer then there other arms, so if you see those features dont buy it if you ever want to see it and interact with you. And they might say its a brown but it most likely isnt.