Filter, Zhang Jianyi, block, sponge, wire mesh, sponge, ceramic ring or something
The ceramic ring is mainly used to culture nitrifying bacteria to achieve the effect of biochemical filtration. Nitrifying bacteria decompose impurities, called non-toxic substances.
The main function of sponge is physical filtration, that is, large particles of impurities intercepted.
Physical filtration, biochemical filtration are needed, so it is recommended to leave at least one layer of sponge, and then put some ceramic rings inside.
