Provided is a system for feeding aquatic organisms in which the maintenance of a cleaning device, a circulating pump and so on can be easily conducted and the size of a cleaning zone can be reduced to give a compact device. A system comprising a water tank (1), a partition wall (2) for dividing the water tank (1) into a feeding zone (11) and a cleaning zone (12), a circulating pump (81) for circulating water between the feeding zone (11) and the cleaning zone (12) and one or more cleaning devices selected from among a filtration device (50) by which water is allowed to penetrate through a filter material and thus filtered, a protein skimmer (70) by which proteins contained in the water are adhered to bubbles and thus removed and an ultraviolet light irradiator by which the water is sterilized by ultraviolet light irradiation. The circulating pump and at least one cleaning device constitute components of a unit. These unit components are loaded on a load frame to construct a cleaning unit (3). As the unit components are loaded on the load frame, the cleaning unit (3) is put in the cleaning zone (12) in an insertable/ejectable manner.