1. Hit the cylinder: Arowana is irascible, but they are timid. There is a loud noise around or someone slapping the fish tank, which will scare them. If they are frightened or uncomfortable, they will bump into the tank. Scales will fall off when hitting the cylinder.

2. Environmental stimulation: It may also be due to environmental stimulation, such as too large temperature difference when changing water or too large water flow impacting fish, which will cause scales to fall off. There is also too much fluctuation in water quality, such as too high frequency of water change or too large amount of water change, which will cause water quality fluctuation. Arowana is sensitive, so when the environment fluctuates slightly, it will produce a larger response.

3. Fighting: Arowana is fierce and has a strong sense of territory. If there are two or more Arowana in the fish tank. They will fight, and the attack power of Arowana is relatively strong, and scales will fall off when fighting.

Arowana scales grow after falling off, because their scales have the function of regeneration, and their scales can be restored to their original state as long as the breeder takes good care of them. Although their scales can be recovered, it takes a long time to recover. Even if they fall off slightly, it will take at least one month or so to grow new ones. If the area of scales is large or the skin is damaged, it will take about 1-3 months.