PROBLEM TO BE SOLVED: To provide a purification device for a breeding aquarium of water organisms, the device that eliminates the occurrence of salt-creep deposits in water containing mineral such as seawater and the closure of an air delivery pipe for feeding air in a filtration tank, and has a high culture function and is used for microorganisms.SOLUTION: A purification device is structured as follows: air is sent from an air supplying hole 2 provided on an upper wall of a microorganism growing box 101 air is sent off from a water air outlet 14 of the lower end of a drainage pipe 11 provided at the other corner of the box through a space generated by air supply and placing an air stone to the water in the pipe the drainage pipe sucks up the water to a salt-creep deposit prevention box 110 and the water is ejected from a discharge hole 10 in the upper part of a water storage tank 111 in communication therewith in an aquarium.
