Ditto on what was said above. Also despite the fact that they turn up in the trade from time to time, it is illegal to import one. I worked at a store that got one "by surprise"... I swear once these creatures enter the country they become a literal "hot potato" through the chain of custody until some unsuspecting retailer (and hobbyist!?) ends up with it.
They are beautiful animals to be sure, short-lived - 2 years approximately. I was fortunate enough to witness the one my former employer ended up with, tend her eggs until they hatched. As is normal with cephlapods, she died hours later. The babies did not survive either as we did not have the means to feed them.
Their bite is lethal - gorgeous creature but definitely NOT worth the risk.
uh - my suggestion of substituting your great white shak with the blue ring octopus was a joke - it is IMO about as appropriate as the Great White in a home tank......Sorry if it was misunderstood.......