When raising guppies, as long as the water quality is in a relatively stable state, there is no need to add any substance to the water. But if the fish are infected with bacteria or parasites, they need to add salt to the water.
The purpose of adding salt is to sterilize. Saline water does not directly kill bacteria, but increases the osmotic pressure of water. Because bacteria are mostly composed of cells, when salt is added to water, the water in bacteria cells will flow to salt water with higher osmotic pressure. Then the bacteria cells will lose water and die, so as to achieve the purpose of sterilization. In addition, because guppies are freshwater fish, it is better not to add salt at ordinary times. When it is necessary to prevent or treat fish diseases, salt is added to remove pathogens.
Adding salt can regulate the osmotic pressure in the water, thus dehydrating the bacteria cells and causing them to die. If the proportion of salt and water is not well controlled, the osmotic pressure in the water is higher than that in the body fluid of the fish, which can also make the fish dehydrate and die. Therefore, the concentration of salt water should not be higher than that of fish body fluid, but higher than that of bacterial cell fluid. The most suitable salt water concentration is 2%, which can remove the bacteria in the water without harming the fish.
