If you’ve ever gotten up in the middle of the night to find your goldfish happily swimming around, you may be wondering if your goldfish ever sleeps.
Some fish are believed to always be awake, but goldfish are one of the species that do, in fact, sleep. A sleeping goldfish is likely to be found sitting on the bottom of the tank not moving (perhaps slowly moving their fins). They will also be slow to react to food or nearby movement.
One thing to be aware of, however, is that what you think of as your goldfish “sleeping” may in fact be a sign of a very dangerous condition that you need to address as quickly as possible.
How Can You Tell When a Goldfish is Actually Sleeping?
A sleeping goldfish will usually be found floating near the bottom of the tank. You may notice your goldfish staying in one spot, moving its fins more slowly. It may also look more pale than usual.
This may be concerning at first, but if this is part of your goldfish’s usual routine, it is nothing to worry about. (Read on to find out when it is a concern.)
Please note that a sleeping goldfish will always be either upright or pointed downward at a slight angle. If your goldfish is completely vertical or upside down, see the section on swim bladder disorder at the bottom of this article.
Do Goldfish Sleep with Their Eyes Open?
Yes, goldfish do, in fact, sleep with their eyes open, as they don’t have eyelids to close. Don’t let this fool you into thinking that they’re always awake, however. As stated above, goldfish are perfectly capable of sleeping – even without eyelids.
While sleeping, they will simply appear like they’re in a trance, hovering an inch or so from the bottom of the tank.
When Do Goldfish Sleep?
Goldfish are usually diurnal fish (sleeping at night and active during the day). This is not the case, however, with all goldfish, and some can be nocturnal (sleeping at night) at random.
Scientists have shown that goldfish are especially likely to become nocturnal if they are fed primarily at night. Goldfish fed during the day, on the other hand, are much more likely to become diurnal.
Even though there are differences between goldfish on when they sleep, a goldfish will usually stick to the same sleep cycle if their conditions are kept stable.
Exceptions do occur in many fish, however, such as when a female lays eggs and may forego sleep for multiple days while tending to them.
Do Goldfish Need Darkness to Sleep?
In goldfish that haven’t adapted to a nocturnal lifestyle, scientists have shown that light does indeed interrupt their sleep. (This is a distinct difference from nocturnal species of fish, which light does not interrupt. I’ve not seen any information dealing specifically with nocturnally adapted goldfish, however.)
Given this, the best advice is that you should provide them 10-12 hours of darkness per night so they can get the amount of sleep that they need.
Sleep Deprived Goldfish
Studies done in zebrafish have shown that fish can indeed become sleep deprived if they don’t get enough sleep.
When scientists kept the fish from being able to sleep when they normally would, they became sleep deprived and needed to sleep in during their next sleep period to make up for the sleep they lost.
They were only able to sleep when it was dark, however, and lights appeared to prevent them from catching up on their much needed sleep.
Is Your Goldfish Sleeping a Lot?
If you notice your goldfish spends all day “sleeping”, this is cause for concern. This may be a sign of ammonia toxicity – a condition that can kill your fish if it isn’t treated as quickly as possible.
This is especially a concern in goldfish, which are notorious for being messy and producing a lot of waste and ammonia.
If you notice these symptoms in your fish, you need to take immediate action:
- Lack of energy.
- Loss of appetite.
- Your goldfish hanging out at the bottom of the tank all day.
- Gasping for air.
This is especially a concern if your fish are in a small tank, you have recently changed most or all of your tank’s water, or you have cleaned or replaced your filter. This can get rid of the bacteria that clean the ammonia out of your tank’s water – causing the water to become poisonous.
If you notice these symptoms in your goldfish, you should immediately test your tank’s water for ammonia, nitrate, and nitrite. If your tank’s levels are too high, you should perform a 50% water change and use a chemical neutralizer.
If you can move your fish to a larger tank that has already cycled, you should do so as quickly as possible. (Fancy goldfish should have 20 gallons + 10 gallons for every extra fish, and slim bodied goldfish should have 30 gallons + 20 gallons for each additional fish.) Otherwise, if you have a vet that specializes in fish care, you should call them for further advice. Failure to take the appropriate action can result in the death of the fish in the tank.
Why is My Goldfish Sleeping Upside Down?
If your goldfish appears to be sleeping on its side, upside down, or vertically (sometimes either floating to the top of the tank or sinking to the bottom), this is not normal (and your fish is not sleeping).
Your fish most likely has what is commonly known as swim bladder disease.
This problem is especially common in fancy goldfish. “Swim bladder disease” is not a single condition and can be caused by multiple things. The most common cause appears to be diet related – with your goldfish getting constipation or gulping air during feeding.
In this case, you can help treat your fish, by withholding food for 2-3 days and afterwards providing frozen peas that you’ve thawed, removed the skins from, and chopped into smaller pieces.
This acts as a laxative, and can often resolve the problem.
Another thing you may want to do is check the water quality of your tank, as mentioned in the above section.
For more information on buoyancy problems (if you believe your goldfish has them), check out INJAF’s article on the topic.
Is My Goldfish Sleeping or Dead?
The surest way to make sure your goldfish is actually sleeping and isn’t dead is to check for gill movement.
While asleep, your goldfish will have less gill movement than while awake. While dead, however, your goldfish will have no gill movement whatsoever. (In which case it’s time to send it to the toilet for a proper burial.)
If your goldfish isn’t dead, however, it may be time to check your water quality, just in case. (If you skimmed directly to this section, read above for more information.)
Rest assured, though, that if your water quality is good, and your fish seems fine afterwards, it’s probably just settling in for a well deserved nap.
Do you have any questions about your goldfish’s sleep habits that I didn’t answer? Leave them in the comments below!