What is sleep, actually?
Sleep is a period of rest during which the body recovers and processes stimuli. In humans and other mammals, sleep is often accompanied by closed eyes, a clear sleeping posture, and a fixed day-night rhythm. Brain activity changes and the body comes to rest. However, not all animals sleep in the same way, and this certainly applies to fish.
What does sleep look like in fish?
Fish have no eyelids and therefore do not close their eyes. Still, they experience rest periods during which their activity decreases significantly. During these periods, they move less, respond more slowly to their surroundings, and often seek out a fixed location. Some fish hover almost motionless in the water, while others hide among plants, stones, in caves, or buried in the sand.
Instead of deep sleep, as in humans, fish usually enter a resting state. Their brain activity changes, but they remain alert enough to react quickly to danger. This makes sense, as fish in the wild are vulnerable to predators. Rest periods therefore occur several times a day and are spread over shorter intervals.
Differences between fish species
How fish rest varies greatly by species. Diurnal fish mainly rest at night, while nocturnal species are less active during the day. Bottom-dwelling fish often seek sheltered spots, while some fish even lie on their side or burrow into the sand. Sharks and some other species must keep moving to allow water to flow over their gills and therefore rest while swimming. How long they actually “rest” depends on the species and can range from short rest periods to as much as six to eight hours per day.
Why is rest so important for fish?
Rest is essential for the well-being of fish. During rest periods, they recover from exertion, process stimuli, and conserve energy. A lack of rest can lead to stress, which may affect behavior, immune resistance, and overall condition. In an aquarium, the environment therefore plays a major role: sufficient hiding places, a logical light-dark cycle, and a calm setup help fish follow their natural rest patterns.
What can you pay attention to yourself?
1. Day-night rhythm and lighting
Light plays an important role in the daily rhythm of fish. In nature, this naturally follows the cycle of day and night, but in an aquarium it is entirely determined by lighting. A fixed and predictable lighting schedule helps fish recognize when it is time to be active and when it is time to rest. Lighting that is too long or irregular can disrupt rest periods and cause restlessness. A clear day-night rhythm best matches the natural behavior of fish.
2. Hiding places and aquarium setup
During rest periods, many fish seek shelter. Hiding places provide a sense of safety and allow fish to rest undisturbed. Think of plants, stones, wood, or specially designed shelters. The need for shelter varies by species, but a varied setup ensures that every fish can find a suitable spot. This contributes to less stress and more natural behavior.
3. Calm surroundings around the aquarium
Not only the setup inside the aquarium but also the environment around it affects fish rest. Vibrations, loud noises, and a lot of movement can be disruptive, especially during rest periods. A quiet location for the aquarium helps fish feel safe and follow their natural rhythm. This way, you create a stable and relaxed living environment.
In conclusion
Fish may not sleep the way we do, but rest also plays an important role for this group of animals. By taking their natural behavior, day-night rhythm, and aquarium setup into account, you can create an environment in which fish feel safe and can rest undisturbed. Even small adjustments can make a big difference in their comfort and behavior.
Do you still have questions about this topic after reading this blog? Please feel free to contact us at: veterinarian@vetsend.co.uk.
