Do Fish Go to Sleep?

If you have experience caring for fish in an aquarium or pond, you may start to wonder if they ever take naps or get some shut-eye. They may always seem to be swimming about and responding to their environment. Since most fish don’t have eyelids, they can’t technically get any “shut-eye,” but whether or not fish fully sleep isn’t clear cut. Researchers are still exploring and understanding what happens in a fish’s body when it enters a resting state, but the consensus is clear that fish do enter into a sleeping state. The way fish sleep isn’t like how humans or other mammals sleep, but it still serves an important function similar to ours. The pond and aquarium experts at Aquatic Warehouse are here to explain how, why, and what it looks like when fish sleep.

Why Fish Sleep

Almost every living organism needs to shift into different states of being to let their bodies rest and repair. The major organs, metabolism, and nervous system all need some sort of recovery phase that’s different from the state of interacting with the world. You can think of it a little like a computer needing to be restarted and updated to keep all the software and functions moving smoothly.

Do Fish Dream?

It’s not entirely clear why fish sleep and which processes are happening when they do, but researchers do know it promotes their health and helps them restore balance. One major difference, though, is that fish aren’t undergoing the same mental processes as humans due to the lack of a neocortex within the brain, which means they aren’t dreaming or entering REM states of sleep.

How Fish Sleep

How exactly a fish sleeps depends on the species. There are many ways fish can enter this restful state, oftentimes depending on the species of fish’s environment, behavior, and natural predators. Some fish lay down and rest at the bottom of the pond or tank. Others may burrow, hiding to protect themselves from predators. They may also hide within their environment, such as between coral. Drifting is another sleeping style for some fish that allows them to stay afloat with little movement. This is common in some aquarium fish, and it may look like they’re just drifting about when in reality they’re sleeping. For fish, there’s a different level of alertness. It’s not like human sleep, where we’re losing consciousness for long periods. Fish remain alert to oncoming activity from predators and can respond to their environment, which is why they may not seem like they’re sleeping when they’re able to just wake up very easily. Saltwater parrotfish actually perform an amazing thing at night. They create, or “spin”, a cocoon that hides them from predators, and their respiration is sufficiently diminished in this suspended state. Predators can swim right by them and not see or sense them. There are only a few species of fish that sleep deep enough to not wake them up at night.

Whether or not fish transcend into a deep sleep may still be up for debate, but one thing’s for certain—you need the right supplies to care for an aquarium properly and create an environment calming enough to let your fish sleep if they will. If you need an aquarium dosing pump, LED lighting, a protein skimmer, or any other essential aquarium supplies, reach out to Aquatic Warehouse. Give one of our friendly and knowledgeable representatives a call today at 858-467-9297.