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Fish sleep

When an aquarium is abruptly switched on in the morning, it is noticeable that it soccupants do not immediately resume a fish normal activity. Some of a fish are on the bottom of the tank, some in the plants, and others remain almost immobilein the water. It is difficult to speak of sleep in the generally accepted sense of theword, but it is certain that fish have periods of restfulness, of varying degrees. This can be verified at night, with the aid of a small flash light: the fish are practically stationary (apart from nocturnal species), but their eyesare not closed as they have no eye lids.

DO FISH RECOGNIZE THEIR OWNER?

Countless aquarists have noticed that some of their fishes react more enthusiastically to their presence than to that of strangers. If fish do "recognize" the person who looks after them, how do they do it? They are capable of distinguishing the special characteristics of the vibrations caused by the foot steps of such and such person,which are transmitted to the water of the aquarium. Not only that, their sense of sight, although not perfect, helps them in this task of "recognition".

DO FISH FEEL PHYSICAL PAIN?

The sensation of pain is sent to the brain via the sensory nerves. As fish are endowed withthe latter, it can be assumed that they feel pain when they are hit or wounded,and perhaps even when they are sick.