hmm... you could always try to find a pump made especially for jellies octopi... i know they have them online somewhere I just can't remember where to find them...
oh btw, if you guys try to attempt another one a great way to keep them in the tank is to put a strip of astroturf around the rim of the lid.... they can't get a grip on the stuff :)
i'm not going to lie... i envy you! the octopus is what got me to want a fish tank in the first place. i think i still want to get a lot more experience before i consider getting one though. thanks for posting! :D