The filter materials that may be used in general aquariums include zeolite, bacteria room, activated carbon, volcanic rocks, seasonable balls, brushes, oyster shells, rattan cotton, coral sand, biochemical balls, glass rings, ceramic rings, medical stone and filter cotton. Not every filter will be used. Because there are many varieties in koi fish, people who raise koi fish will have a higher density of raising koi fish, so it is very important to filter and raise koi fish filter materials.

(1) Plant filtration: it is mainly a method of using plants in water to absorb harmful products in water. Common plants in water are duckweed and Acorus gramineus. Their roots are well developed, and they can absorb iron ions and pesticides in water in addition to plant filtration. Using plant filtration can reduce the harm of harmful substances to koi fish.

(2) Physical filtration: dust, colloid, suspended matter, leaves, etc. are mainly removed by various filtering materials. To keep the water transparent. The traditional simple method is to use sand and gravel particles to make water permeate and remove suspended solids visible to the naked eye. At the same time, it has dual functions of physical filtration and biochemical filtration.

(3) Chemical filtration: filter materials are mainly used to dissolve various ionic compounds and odors. It is harmful to koi fish in water. Commonly used filter materials include phosphate rock, activated carbon and medical stone.

(4) Biochemical filtration: mainly using nitrifying bacteria attached to the filter material to oxidize nitrogen-containing organic matter or ammonia and residual food residues produced by koi fish. It is the most important part of the whole fish pond filtration system. Commonly used filter materials include brush, fiber cotton, biochemical silk, biochemical ball, etc. Be careful not to kill nitrifying bacteria when cleaning the filter material or filter tank.

The filter materials commonly used in koi fish for fish tank culture will not include brushes, rattan cotton and large mushroom houses, but all the filter materials can be used in fish pond filter ponds.