How does bottom filtration work in a fish tank? Preferably with a diagram of how the feces is sucked up?

The working principle of the fish tank bottom filtration is to make the water from the main tank enter the filter tank by overflow or siphon, and then pumped back to the main tank by the pump after filtered by the filter tank material.

See picture: ?

Overflow

Siphon

The fecal matter is now in the bottom tank with the water flow.

Expanded Information

Filtration Methods

Current filtration methods are: physical, biological, chemical, etc. They will work non-stop as long as they are plugged in.

The filter must have 2 or more filtration methods: physical filtration, biological filtration, chemical filtration

Physical filtration: it is the use of mechanical methods to isolate the larger particles in the water. Such as the remaining feed particles, dead fish bones, fish excreta, secretions, vomit, body mucus, etc., generally use sponges, spray cotton, fine mesh nylon mesh, palm leaf fibers, etc.. It is usually set at the initial end of the filtration system for easy cleaning.

Biological filtration: Cultivate beneficial bacteria bacteria, through the bacterial decomposition of harmful elements, such as: ammonia salts, nitrite, nitrate, phosphate, etc.. Commonly used filter media are: biochemical ball, ceramic ring, glass ring, coral sand, etc. (the most important filtration method, to maintain the ecosystem)

Chemical filtration: it is the use of chemical agents to remove impurities in the water, the agents used are water quality stabilizers, flocculating agents, algaecides, protein decomposition, deodorizers and so on.

Adsorption filtration: it is wood, coal, shells, animal bones and other substances with very high carbon content can adsorb seawater proteins, trace elements, decolorization, in addition to odor, even the molecules of ozone can be absorbed by it. Fish urine, microalgae in the water as well as drugs can also be adsorbed by it

Because nitrifying bacteria must live with flowing water in the filter cotton, glass ring or bottom sand, so the filter should be open 24 hours.

Baidu Encyclopedia - Fish Tank Filter