Fish need sleep just like every other animal. It is essential so that they stay healthy and function normally. Now that we know fish do not sleep upside down, you are probably wondering how they sleep.
When fish sleep, they do not lie down but float relatively still near the bottom of the tank. They may appear awake because they will move their body slightly, but they are not. This slight, constant movement of their fins or body creates water flow across their gills to keep their oxygen levels consistent.
Interestingly, fish go through similar sleep cycles as us humans. In fact, a large body of research focuses on fish and their brain activity during sleep to be related to humans – thanks to the likeliness of their sleep cycle to ours.
The sleeping habits of fish differ. Some fish will hover at the bottom, some float at the top, some bury in the sand, and others swim slowly around the tank.
You can see if your fish is sleeping through their reaction time. If you place food in the fish tank and your fish takes a while to respond, it is because they are sleeping. Another way to identify a sleeping fish is to watch them for a minute – if they are still in the same position after that time, they are sleeping.