Who has an aquarium at home always wonders: How do fish sleep? In some situations, it is possible to observe the fishes at the bottom of the aquarium moving slowly and we do not know whether they are sleeping or not.

Each species of fish has a different habit, some rest resting on the rocks and others are on the surface, as is the case with the butterfly fish. However, his eyes are always open by the absence of eyelids.

Only when these animals feel safe and realize that they can rest peacefully, alternate periods of rest and wakefulness. When they are at rest they are in a shallow state of immobility, where their movements are extremely slow to maintain balance.