When you share your home with another creature, it’s natural to be curious about their lives and how they experience the world.
Your goldfish might live in an aquarium, rather than sleeping on your couch like a dog or cat, but they’re still your pet and your responsibility.
One of the things you might be wondering about is whether goldfish sleep?
Well, the short answer is “yes,” but there’s more to it than that.
In this post we’ll attempt to answers any questions you might have about goldfish sleeping habits.
How Can You Tell When Your Goldfish is Sleeping?
It’s not like goldfish put their pajamas on and tuck themselves into bed, so how can you tell when they’re sleeping?
Well, if your goldfish is floating still somewhere near the bottom (an inch or two above the substrate) or middle of their tank, with their fins relaxed and spread out, and their head pointed slightly down, they’re probably sleeping.
You may also notice their coloring looks somewhat more dull than usual. They may still move slightly when sleeping, just to maintain their balance.
If Your Goldfish is Floating Around With Open Eyes, Could They Be Sleeping?
Your goldfish is floating quietly in the middle of the tank but has their eyes open, so they couldn’t be sleeping, right? WRONG!
Goldfish actually don’t have eyelids, so they must sleep with their eyes open and you’ll never catch them snoozing with their eyes closed!
Are There any Alternative Sleeping Positions for Goldfish?
You might be wondering if a goldfish floating right on top of the water, on their side or back, or down low on the substrate could be sleeping. The answer is probably, no. It’s more likely that they’re unwell, or there’s something else going on.
If floating right up on the surface of the water or on their back or side, they are likely to be suffering from buoyancy issues caused by swim bladder disease or similar.
A goldfish that remains right at the bottom of the tank for a long time could be suffering from an illness or infection, or there could be an issue with the water quality in your tank.
If in doubt, consult a veterinarian that specializes in fish.
Do Goldfish Sleep as Deeply as Humans?
Although it’s difficult to compare phenomena like sleep between hugely different species, it’s likely that goldfish don’t sleep as deeply as humans. A couple of things back this up.
Firstly, current research suggests that fish (and most other cold-blooded animals) don’t cycle through different sleep stages and don’t experience REM sleep. REM is the deepest stage of sleep for humans and other mammals, so it’s probable fish experience lighter sleep overall.
It’s also notable that goldfish’s brain waves don’t change when they sleep, unlike humans whose brains waves change from beta and alpha waves during periods of wakefulness to theta and delta during sleep.
This suggests the sleep state of a goldfish isn’t as deep as that of a human. In fact, it might be more like what we’d consider resting.
Do Goldfish Dream?
Since goldfish sleep, do they dream?
Scientists used to believe that humans (and other animals) only dreamed during REM sleep, it’s now known that we can dream in various stages of the sleep cycle.
However, dreaming is characterized by a shift in brain wave activity, and goldfish’s brain waves don’t change when they sleep, so it’s unlikely that they dream.
That said, it’s impossible to tell for certain, so there’s a small chance that your goldfish is dreaming about fish flakes and owning their own castle when they snooze.
Can Goldfish Hibernate?
Yes, goldfish can hibernate, but those kept indoors don’t.
Wild goldfish or those kept in outdoor ponds go into hibernation when temperatures drop low enough. They drop to the bottom of the pond, more or less stop moving, and their metabolism slows right down, which conserves their energy during cold periods where there may not be much food around.
If your goldfish looks as though they’re hibernating (has stopped eating and moving) but you keep them indoors, it’s likely that they’re unwell.
Do Goldfish Sleep at Night or in the Day?
While you might occasionally catch them napping during the day, goldfish are generally diurnal, meaning they’re awake during the day and sleep at night.
Just like us, goldfish sleep better when it’s dark and may have trouble telling the difference between day and night if his lights are on all the time. That’s why it’s vital that the lights in their tank are switched off for at least 12 hours a day (in a continuous stretch).
This will help your goldfish get into a day/night cycle and have a better night’s sleep.
What Should I do if My Goldfish is Sleeping?
If you spot your goldfish sleeping, leave them alone!
If you make any sudden movements close to their tank, switch on their lights, or feed them when they’re asleep, you may startle them.
While it’s probably not an issue if it happens once or twice, startling your goldfish causes undue stress, which can ultimately lead to illness. Plus, nobody likes to be woken from a nap!
Happy fish keeping!