The main purpose of putting salt in feed water is to regulate osmotic pressure and achieve sterilization at the same time. The salt content of normal feeding water is very low, while the body fluid concentration of fish is 0.5%. The two concentrations are different, so they will produce osmotic pressure. Water will flow to the higher osmotic pressure area, that is, the fish body. In this case, the fish will drink a lot of water, while excreting salt in the body, to maintain the consistency of concentration inside and outside the body. This will increase the burden of the fish, which is not conducive to the growth of the fish. Therefore, it is necessary to add salt to the water to adjust the osmotic pressure. It is better to control the concentration of feed water at 0.5%. It is consistent with the concentration of fish body fluid, which can make it in the most comfortable state. Another purpose of adding salt is to kill bacteria. When the concentration of water environment is high, due to the role of osmotic pressure, bacteria can be dehydrated and die, thus achieving the role of sterilization.
How much salt is appropriate depends on the amount of water they are fed. In order to reduce the effect of osmotic pressure on fish, it is suggested that the concentration of feed water should be adjusted to be consistent with its body fluid concentration. The specific amount of salt added needs to be determined according to the amount of feeding water. As long as it contains 5 grams of salt per kilogram of water. In addition, the salt put into the water can not use edible salt, otherwise it will lead to iodine poisoning of fish. Crude salt is generally used to adjust the concentration of feed water.
