Each time the electric eel at the Aqua Toto Gifu aquarium touches a copper wire in its tank, it sends power that lights up globes decking a Christmas tree.
Officials expect the "eel Christmas tree" to be a popular attraction for dating couples in the lead-up to Christmas Day, when the tree will be removed.
Electric eels are capable of generating electricity in their bodies. They have notoriously poor eyesight and use electric shocks to stun prey so they can catch and eat them.