The present invention relates to an automatic water restitution system for a saltwater fish aquarium which is capable of restituting seawater automatically to maximize the convenience of the seawater management. The system includes: a sea salt supplier (20) which discharges the sea salt (ts) stored on the inside through a sea salt input means (22) a seawater tank (30) which is mixed with the water and the sea salt to prepare the seawater a farming tank (40) which receives the seawater from the seawater tank (30), discharges the existing seawater, and farms marine fish a second water level sensor (P2) sensing the water level of the farming tank (40) and a controller unit (50) which controls the operation of the sea salt input means (22) of the sea salt supplier (20) to adjust the amount of the sea salt discharged to the seawater tank (30), adjusts the amount of water flowing into the seawater tank (30), receives a sensing signal from the second water level sensor (P2) in order to restitute the seawater in the farming tank (40) to adjust the amount of seawater discharged from the farming tank (40) and the amount of seawater supplied from the seawater tank (30). The present invention supplies new seawater to the farming tank (40) at preset time, discharges the existing seawater including a contamination source of the farming tank (40) to the outside, thereby automatically restituting the seawater in the farming tank (40). Accordingly, the present invention can maximize the convenience of the seawater management. The present invention can create an optimal habitat environment for the marine fish and safely farm the marine fish without diseases.COPYRIGHT KIPO 2016본 발명은 해수를 자동으로 환수(물갈이)되도록 해 줌으로서 해수관리의 편의성을 극대화할 수 있는 해수어 수족관의 자동환수시스템에 관한 것으로서, 내부에 저장된 해수염(st)을 해수염 투입수단(22)을 매개로 배출하는 해수염공급기(20)와 상기 해수염(st)과 물이 혼합되어 해수가 제조되는 해수탱크(30)와 상기 해수탱크(30)로부터 해수를 공급받고 기존 해수는 배출되며 해산어류를 양식할 수 있도록 된 양식조(40)와 상기 양식조(40)의 수위를 감지하는 제2수위센서(P2)와 상기 해수염공급기(20)의 해수염 투입수단(22)을 동작제어하여 해수탱크(30)로
