PROBLEM TO BE SOLVED: To provide a purifier which is highly efficient compared with a conventional system, and which, with the intension of constructing the same mechanism as an efficient purification system that a river has, creates water circulation corresponding to the water circulation in the natural world caused by vaporization of water and rain using pump means, and generates a water flow in a biological filter layer consisting of a useful purification bacteria group, and an aquarium in which the purifier is integrally incorporated.SOLUTION: A purifier includes a low water-permeability biological filter layer 3 for purifying water, and pump means 5 for generating a water flow in the biological filter layer 3. The biological filter layer 3 is a useful purification bacteria group where bacteria for purification grow, and the useful purification bacteria group is fixed in a bulk state.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2017,JPO&INPIT
