Aquarium staff have managed to wean a chocoholic giant fish onto a healthier diet after inheriting the gourami, raised entirely on Kit Kats by its owners.
At first, staff at the Sea Life London Aquarium were baffled by the 4kg fish's refusal to eat until they learned it had been fed nothing but chocolate.
The team then stuffed crushed Kit Kat pieces inside grapes to get the 40cm-long gourami named Gary to "take a break" from his daily fix.
"I have never heard of a fish being fed chocolate, let alone being brought up entirely on the stuff," said Gary's handler, Rebecca Carter.
"Gouramis usually eat a diet of fruit but Gary doesn't appear to have suffered any ill effects from his chocolate addiction," she added.
"However, we would not recommend feeding fish confectionery of any kind."
Gary is not the only unusual creature to come to the centre from private owners.
Close by the gourami lives Ed, a catfish with decidedly cat-like tendencies.
Ed will only accept being hand fed and likes to be stroked on the head at the same time.
He has also learned to head-butt a lethal puffer fish who vies for his food, staff said.
But aquarium staff warn that Gary and Ed's peculiar interest in food highlights a more serious issue.
They have nicknamed one display the "tank busters" tank, because it houses a number of large fish that simply grew too big for their owners to manage.
"Many people don't do the right research when they buy fish and end up unable to care for them," said Ms Carter.
"We're delighted we could find a home for Gary but the fact is we simply do not have the space to accommodate the vast number of re-homing requests we receive."