hi - i am not the right person to fully answer this, bc i am just hoping to own one soon, but in the research i have done for it so far, i learned that it takes 3 months for an aquarium to mature so that an octopus can even live in it. do you already have a tank set up? also, it needs to be 55gallons minimum with lots of live rock, caves and other such hiding places. if you dont have this set up already he isnt going to live long.
btw - where did you buy your octo? i are you located in larval mass, bc i am in boston and really have done a lot of research but cant find anyone selling them in boston. would def like to learn more about how you found yours.
good luck!
zoe