1. Reason: Goldfish may turn black because they are not treated in time after injury, and their body surface is fragile, so they are prone to injury. In addition, if the breeding density is too high, it will also lead to their physical injury.

2, Solution: Breeders need to change their water immediately, so as to avoid wound infection. Also add some crude salt to the fish tank, which can inhibit the growth of bacteria. If the wound is serious, the breeder had better apply some anti-inflammatory drugs to them.

1. Reason: Goldfish's blackening may be caused by being frightened, and they are very timid. If someone slaps the fish tank hard or makes a loud noise, goldfish will easily be frightened. When they are frightened, the color of their bodies may turn black.

2, Solution: Breeders need to keep their surroundings quiet first, so that they can recover from the frightened state. Feed them with some color-enhancing feed, so that they can keep their body color.

1. Reason: Goldfish may also suffer from black spot because of blackening, and the main cause of black spot is bacterial infection. Goldfish suffering from black spot disease will have black spots on their bodies.

2. Solution: Breeders need to isolate sick goldfish to prevent them from infecting other fish. Also use potassium permanganate to give them a medicated bath. If you stick to the medicated bath for a few days, the black spots will become shallow.