There may be several reasons why fish sleep with their eyes open:

1. Fish sleep with their eyes open because fish have no eyelids and cannot close their eyes while sleeping.

2. Fish are affected by eye masks and live in dark water for a long time, causing their eyes to become myopic.

3. Under normal circumstances, when a fish swims sideways, floats up or swings its tail, it may mean that the fish is sleeping.

Fish sleep for a short time and are very alert, and will wake up at the slightest movement. When a fish sleeps, it will stop swimming and remain motionless. If the fish's eyes are closed, it will die.

Tip:

Different fish have different resting times. In addition, fish sleep in various postures. Some like to rest in the sand, and some like to hide behind aquatic plants or rockeries. Among the fish, there is a kind of parrotfish. When they sleep, they blow a bubble and then get into the bubble to sleep.