From the Mercury News:

The story goes that an unspecified aquarium somewhere in the United States was losing fish from a particular exhibit at a rapid pace.

For days, keepers wondered why the fish were disappearing. They weren’t the kind of fish that would eat each other, and no one was breaking in with a pole and tackle box. Finally officials decided to film the tank at night to see if they could catch the culprit.

Which is why the back of the tank holding the Giant Pacific Octopus at the Monterey Bay Aquarium is now lined with AstroTurf. The buggers can’t get their suckers to stick to the material and pull themselves out of the tank, after which they could scurry across the floor, pop into another tank and indulge in an unauthorized midnight snack.

Instead, to keep them busy, food is often placed in round containers resembling hamster balls. Retrieving the food is like a puzzle for the octopus, keeping its brain exercised and otherwise occupied from formulating escape plans.

[To the tune of The Beatles, “Octopus’s Garden,” from the album Abbey Road (a 2-star song, imo).]