The two pieces on the koi's nostrils are used to help it smell. The piece on the fish's nostril is called the "nasal valve". If you look closely, it actually grows in the middle of the two fish nostrils, dividing the nostril into two small holes. The water hits the nasal valve, flows into the front opening, passes through the "olfactory receptors", and then flows out from the back opening, so the fish can smell it. Most bony fish have had this kind of nostril structure from ancient times to the present.

How to raise koi carp

1. Prepare a fish tank of appropriate size. Decorative water plants should be placed in the fish tank. The fish tank should be made of non-toxic materials.

2. A filtration system and an oxygen generator must be installed in the fish tank. The filtration system must filter four times an hour to ensure the health of the koi.

3. Change the water in the fish tank regularly and clean the filtration system and oxygen generator. If it is not cleaned for a long time, it will lead to water pollution in the fish tank and also cause the filtration system and oxygen generator to stop working.

4. Feed a certain amount each time. Feeding too much will cause pollution in the fish tank and affect the living environment of koi. Try not to keep koi carps mixed with other fish. If you must keep them together, pay attention to them to prevent fights.