Dwarf species are sometimes kept in 10 gallon tanks in labs, but these tanks are very well cycled and over-filtered. You'll do much better with a 30 gallon - that gives your octopus room to explore and offers you a bit more margin for error.
I certainly hope I didn't come across as calling you "hopelessly naive"...I enjoyed my times with the blue rings, but as Nancy stated, it is more fun to work with an animal that you can really interact with.
That being said, the blue rings that I've kept were maintained in medium sized tanks, with wetdry systems and skimmers, a lot of live rock, and power compact lighting.
The plexiglass lids were secured using nylon thumb bolts, cutouts for overflow and return pipes were wrapped with black duct tape.
Salinity was 1.025, temperature was 78 daytime, 75 nightime.
I never had any problems with them, other than a streak of aggression that is common in all the dwarf species...raising the two front tentacles is a prelude to biting behaviour. Of course, you can't clean the tank with your hands at any time, and will have to rely on sponges on sticks, etc...to me, it was just too much of a pain in the rear, so I moved to more placid species.
Anyway, best of luck, and be sure to keep us posted.
I hope I didn't come across as overly harsh either; in fact, the emphasized "this animal can kill you" part was really aimed at people who might be looking through the archives later for information to decide on whether to keep a blue ring or not. I'm not horribly opposed to people learning the details and deciding they'd want one with full knowledge, but I've now seen a number of sellers who either downplay or don't mention at all that if this animal bites you, it is far more likely to be fatal than, say, a rattlesnake or a scorpion. In 1987, I was looking into getting an octo tank, and the store I went to said "the one you really want is the blue ring, it's prettier." I was fortunate enough to know (in those pre-internet days) to ask "isn't that the kind that can kill you?" And he just had sort of a "well, yeah, but it's prettier, and most people aren't bothered by that." I really got the impression that some sellers care a lot more about the "pretty costs more" markup than they do about not killing their customers.
Anyway, if you, or any one else, have read all the articles like http://www.thecephalopodpage.org/bluering1.php and want to keep one knowing that, I just want to help make sure it's done responsibly. (Pragmatically speaking, since that article says that 1000 blue rings are imported to the US anually, apparently they don't actually bite and kill their owners too often, so owning a blue ring is probably statistically less likely to kill you than riding a motorcycle, but trying to hedge your bets seems like a good idea if you're interested in either of those hobbies.) I actually thought the blue-ring video that Clownfish (I think) posted the other day was pretty nifty, but I don't think they're any cooler than any other octopus. And they're not agressive enough to put in the moat to ward off attackers; I think a school of humbodts would be much more effective as a burglar deterrent and to dispose of your enemies, so what's the fun of having a toxic animal if you can't dispose of pesky British agents trying to foil your world domination plans?
Actually, that does raise the question of what the appeal is for keeping blue rings... I know I'm fascinated by dangerous animals, but I don't have much interest in having them around my house. (But I do want to scrape together the time and money to dive with humboldts, so clearly I'm as much of a Darwin Award candidate as the next guy...) I'm curious what the appeal is, not just for Hobokin but Greg and Roy (and anyone else who's interested in them).
It's also really important to keep stressing how toxic they are because a lot of kids read these pages. Every time the subject of blue rings come up we need to assume that the person interested is juvenile and irresponsible, (and sometimes that can describe a 24 year old).. It's better to risk offending someone than to inadvertently encourage someone who should not be encouraged.
i wasn't offended at all and it wasn't a big deal. i just wanted constructive advise rather than reading how poor my setup design was. things taken into consideration, i talked to lfs and delayed my order. it was supposed to arrive tomorrow, although it was not on their invoice for tomorrow's delivery. i had prepaid for blue ring, but after talking with store owner, we decided that we'll wait till setup is done correctly. so, i have a 40g that was setup for freshwater lying around and i could put some work into that and octo proof it....
or i can design my own acrylic tank and have another lfs guy make it for me (unless anyone here can design and manufacture one, maybe with a little know how on preventing octo escapery). if i go this route, then i can have main tank in the 20-30g range, maybe have an overflow into a rear chamber that has tubing to a seperate sump/refugium. then, have the top completely sealed except for a small cutout with a lid that could be locked into place.
i am not the diy type, so if anyone has ideas, cunstruction plans etc....i would be more than willing to heed advise.