Goldfish sleep with their eyes open. This is because goldfish have no eyelids, so they cannot blink or close their eyes. A goldfish sleeping with its eyes open can easily be confused with death. The owner can judge whether the goldfish is dead by observing its gills. The trembling gills prove that the goldfish is still alive.

How do goldfish sleep?

1. When goldfish sleep, their eyes are open, but their bodies remain still.

2. Although their bodies are still, their mouths remain slightly open.

3. Some goldfish will hide in dark places and remain motionless at night. This is a normal sign of their rest.