How to treat the abnormal sound of the valve regulating water flow in the bottom filter of fish tank?

There are three kinds of noises in the bottom filter cartridge:

1. The water from the sewer pipe impacts the water surface of the bottom cylinder. Solution: lengthen the sewer pipe so that the outlet is lower than the water surface of the bottom cylinder.

2. The air from the overflow tank is sucked into the sewage pipe. Solution: Install a valve in the sewer pipe, and adjust the flow rate to make the liquid level in the overflow tank have a certain height. Air will not be sucked into the sewer, so there will be no noise.

3. The falling water in the master cylinder impacts the water surface in the overflow tank, resulting in noise. Solution: Raise the water level of the overflow tank. Or add a cotton filter at a certain height in the overflow tank to buffer the falling water.