To solve the problems that a conventional aquarium is square and when the aquarium is placed at a corner of a room, the aquarium can not be admired from the front and the tank is difficult to be decorated because equipment such as pump is only installed in the aquarium.

This water tank body is formed into triangle or formed so as to be able to recognize as triangle in general and acute angle part of water tank body produced by forming into triangle is eliminated by providing partition or rounding or forming into pentagon by using acute angle as face and a pump 5 installed at one angle of triangle and a partition 13 which becomes boundary to water tank is installed in the front of the pump so as to make the pump invisible when admired.