how very exciting ... here is specialist octopus site: http://www.tonmo.com/ sure i have read article by staff at waterzoo about keeping octopus and how difficult it is - think that is local to fishy-fishy, she might know more
It would be a good idea to establish what kind of octopus it is if you can, a photo would be really good. You are dead right Cathie, a guy at my LFS used to keep octopussies (octopii? whatever ) and he has an equipment list here- http://www.waterzoo.co.uk/Staff/Octopus%20aquarium.htm
Thanks to a series of events I won't go into here (they are all in another post) I have ended up with a green brittle (or is it bristle, I've not worked that out yet) star. Despite the risk of it eating anything else I put in the tank in the future (it is currently happy to eat crab pellets but leaves my two hermits, mostly, in peace) I like it. It moves like an octopus over the ground and watching it pick up and eat food is pretty cool.
I also seem to have a load (at least 10) mini stars that must have come on the LR. About 2 inches across, very fine legs, brown or perhaps black with lighter coloured hoops around the legs. I thought they were worms as I only saw one leg at a time - until one came out of it's hidey-hole one day.