Interested in an octopus

I saw some pictures of some octopuses feeding and just swimming. Well, it got me interested in them. I would like to learn some more about them. I know that they are difficult to care for, dont live long, can put out ink, and cant live with much. I just got a compleat 29 gallon and magnum canister filter for $20 so I was thinking I could maybe put one in there. The only saltwater I have delt with is in books while reading about tanks. I could keep up on w/c but dont know if they would be good for me. Any imput would be great.:)