To provide a device and a method for feeding aquarium fish while improving both a feeding efficiency without sparing the feed and a prevention of the pollution of the water in a water bath.

An aquarium fish feeding device for feeding aquarium fish 11 kept in a water bath 10 comprises: a cylinder 2 having a side wall arranged with inflow small holes 21 and 22; and a metallic feeder 3 disposed at the lower end of the cylinder 2 and made diametrically smaller downward to have a feeding small hole 33 at its lower end crest. The water to flow inward from the feeding small hole is made to flow out through the feeding small hole establishes a convection to drop the food for the aquarium fish into the lower end top of the cylinder by making use of a convection established by flowing down the water through the feeding small hole.