The present invention relates to a safety water changer for an aquarium which is connected to and installed in the aquarium to discharge water, which is transferred by an underwater pump installed inside the aquarium, to the outside when the water level of the aquarium maintains a given level, and to supply clean water from the outside to the inside of the aquarium and to block the discharge of the water transferred by the underwater pump to the outside at the same time when the water level of the aquarium drops under the given level, thereby capable of improving a general aquarium as an aquarium which can automatically and safely perform water exchange by receiving new water from the outside and discharging a predetermined amount of water in the aquarium corresponding to the amount of water supply. A float, which is connected to and installed in the one side of the present invention, blocks the lower sides of a water inlet and a water outlet formed in a body to stop supplying clean water from the outside to the inside the aquarium, and allows the discharging of the water inside the aquarium to the outside though the water outlet, which is connected to a discharging pipe of the underwater pump through a connecting pipe, when the water level inside the aquarium maintains a given level. A float, which is connected to and installed in the other side of the present invention, releases the blocking state of the lower sides of the water inlet and the water outlet formed in the body to allow clean water supply from the outside to the inside the aquarium, and blocks the water discharging to the outside through the water outlet, which is connected to the discharging pipe of the underwater pump through the connecting pipe, when the water level of the aquarium drops under the given level.COPYRIGHT KIPO 2014본 발명은 수족관 내에 연결 설치하여, 수족관 내의 담겨 진 물이 일정 수위를 유지할 경우에는 수족관 내에 설치되어 있는 수중펌프에 의해 전달되어 오는 물을 수족관 외부로 배출하고, 수족관 내의 담겨 진 물이 일정 수위 이하로 줄어들 경우에는 수족관 내에 외부로 부터 깨끗한 물을 공급함과 동시에 수중펌프에 의
