[Problem] To provide a fish tank system that makes it possible to maintain and manage the temperature of culture water, without depending on conventional heat source equipment, by using natural geothermal heat and sunlight as the heat source. [Solution] In this fish tank system 10, a culture water tank 18 is placed in a building 14 having a function to inhibit heat transfer with the outside air. A heat insulation water path 20 for inhibiting heat transfer between a ground surface region inside the wall of the building and a ground surface region outside the wall is buried, from the ground surface to a depth of several tens of centimeters to several meters, under the building 14. Constant-temperature ground water is pumped up and allowed to flow through the heat insulation water path 20 to prevent the temperature of the ground region outside the building wall, which follows the ambient temperature, from being transmitted to the inside of the building. Water is circulated between a sunlight sterilization/heating device 12 and the culture water tank 18 to supply water sterilized and heated by sunlight to the culture water tank 18 and adjust the temperature of water in the culture water tank 18 to a temperature suitable for culturing fish.Linvention fournit un système de récipient deau pour poissons vivants qui met en œuvre la chaleur géothermique et la lumière solaire présentes dans la nature en tant que sources de chaleur, et qui permet ainsi de gérer et maintenir la température dune eau délevage sans mise en oeuvre déquipements de source de chaleur conventionnels. Le système (10) de récipient deau pour poissons vivants de linvention est tel quun récipient (18) deau délevage est disposé dans une construction (14) dotée de fonction disolation thermique bloquant la conduction thermique avec lair extérieur, et une conduite (20) deau thermiquement isolée bloquant la conduction thermique entre une région sol dans les murs et une région sol à lextérieur des murs de la const
