If the fish's body turns black, it is necessary to change its water immediately, raise the water temperature appropriately, and feed it with nutritious feed. If you lose your appetite, you need to send it with insecticide. There are many reasons for the blackening of fish, which may be caused by the deterioration of water quality, which requires timely water change to improve the water environment. It may also be a long-term lack of nutrition, so it is necessary to change the food you feed, and you can feed some red worms, bumper shrimp, etc. It may also be the temperature, pay attention to control the water temperature.

1. Water quality changes: When water quality deteriorates, fish will also be stimulated, thus making their body color turn black. This kind of situation is quite common, and it is simple to treat and prevent it. As long as you pay attention to changing water and improving the water environment at ordinary times, the fish will recover soon.

2. Malnutrition: If the food eaten by fish for a long time is not nutritious, it will also cause it to fade. For example, parrot fish will encounter such a situation, which indicates that the body lacks some hair color substances. It is actually very simple to improve it, just change some food with pigment.

3, sudden drop in temperature: Fish will turn black, which is usually related to temperature, especially tropical fish, which has certain requirements for water temperature. If it is lower than 20 ℃, the body will be stimulated, resulting in its blackening. In this case, the best solution is to heat up properly, but not too much in one day.