The invention discloses a simple water changing and cleaning device for a fish tank. The simple water changing and cleaning device is characterized in that a bottle cap is arranged at a bottleneck ofa plastic bottle, two holes are reserved in the bottle cap, one end of an exhaust pipe penetrates through one of the two holes, one end of a water guide pipe penetrates through the other of the two holes, and then sealing treatment is conducted; a one-way air valve is arranged at the upper end of the exhaust pipe, and only allows air to pass through from bottom to top; the middle of the water guide pipe is a bendable hose, the end of the water guide pipe is a hard guide pipe, and cleaning fan blades are arranged in the hard guide pipe. According to the specific composition of the cleaning fanblades, multiple cleaning hairbrushes are arranged at one end of a main shaft rod, and the main shaft rod is provided with a limiting connecting rod to guarantee that the cleaning hairbrushes can freely rotate in a horizontal plane but cannot shake in the vertical direction; the other end of the main shaft rod is provided with a spiral stress face, and the spiral stress face drives the whole cleaning fan blades to rotate under the impact effect of water current. The simple water changing and cleaning device for the fish tank does not contain components of electric appliances, does not need tobe driven by power, and is safe and reliable; the device is simple in structure, and the problem that in the traditional water changing process, water is splashed in all directions, and the environment is polluted is solved.