The question of whether or not do goldfish sleep is not as simple as one might think. While goldfish do, in fact, sleep, they do so differently than humans and many other animals. Since goldfish have no eyelids, their eyes remain open when they are asleep. A more appropriate description would be to say that goldfish rest at certain times during the day and most of the night.
A good indication of goldfish at rest or “sleeping” is when their bodies are observed hovering or tilting a bit with their heads pointing down. There will be less fin activity than when awake, and they tend to hover and gather near the bottom of their tank or fish bowl.
Goldfish will become less active when at rest and only move enough to stay afloat in the water. It is also quite common for goldfish to exhibit a change in their coloring while resting.
Another consequence of goldfish not having eyelids is that they remain reasonably alert even though they are “asleep.” As a result, sudden movements, changes to their environment, and/or lighting can disturb their “sleep” cycle. This, in turn, can cause the fish stress and affect their overall health. Goldfish, much like humans, sleep better in a dark room or environment. Therefore, it is recommended that goldfish are kept in darkened areas of the home, and if housed in tanks or aquariums, the lights should be switched off for at least twelve hours a day. Goldfish are diurnal, meaning they are most active during the day. Nighttime is not a goldfish’s preferred time to rest but they do prefer darkness to light.
You can see goldfish sleeping in this nice video:
But in some cases, goldfish can really seem like they sleep, or let’s say sleep upside down. This is in most cases called swim bladder disease. Swim bladder disease is an illness caused in most cases by a virus or bacterial disease although it can also be caused by improper feeding. When goldfish get swim bladder disease they tend to swim upside down or in this case they stay on the bottom which most of us comprehend like our goldfish is sleeping. You can find out more about swim bladder disease and how to treat it here.
Goldfish are diurnal animals by nature. As such, they are most active during the day and prefer to rest at nighttime. In this vein, their sleep pattern mimics those of most humans.
So to sum it up, Do goldfish sleep?:
- Yes they do, but not in same way as we are sleeping
- They sleep always with their eyes open
- Color of your goldfish can fade a little while sleeping
- They mostly rest/sleep while lights on your aquarium are off (don’t leave your lights more than 10 hours)