1. Reason: The blackening of Arowana scales may be due to the great fluctuation of the environment, and Arowana has higher requirements on water temperature and water quality. Moreover, they are also sensitive to environmental fluctuations. If the water temperature and water quality fluctuate too much, they may have blackened scales.

2. Solution: Breeders need to keep the water temperature constant, preferably using heating rods to keep the water temperature between 28-30 ℃. The PH value should be kept between 6.5 and 7.5, and the amount and frequency of water change should not be too high to avoid fluctuation of water quality.

1. Reason: The blackening of Arowana scales may be caused by feeding too many loaches, although Arowana prefers to eat loach. Moreover, loach is also helpful to their growth and development, but if the feeding amount is too large, their scales will turn black.

2. Solution: Breeders need to stop feeding loaches, so as to prevent their scales from becoming blacker. We should also feed more small fish, shrimps, red worms and other foods to make their body colors more bright.

1. Reason: The blackening of dragon fish scales may also be infected with bacteria. If the water quality is too poor or the scales are not treated in time after trauma, they will be blackened.

2. Solution: Breeders need to use oxytetracycline, penicillin, etc. to give them a medicated bath once a day, and the medicated bath can relieve it for 3-5 days.