Clownfish Sleeping Behavior – Everything You Need to Know

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We never ponder fish sleeping behavior until we get our first aquarium. If you just got your first pair of Nemos, you might wonder: “Do my clownfish need sleep?”

And the answer is a big “Yes!” Clownfish need daily rest to recharge their energy and stay healthy.

But how much is enough, and how do you ensure your pets get the sleep they need? How do you know when your clownfish are sleeping?

Keep reading to find the answers to these questions and more! This article covers everything you need to know about clownfish sleeping habits.

How do Clownfish Sleep in the Tank?

Clownfish are a peculiar species for so many reasons. If you expected their sleeping behaviors to be strange, you wouldn’t be disappointed.

First, a clownfish sleeping is almost indistinguishable from an alert fish. When they want to get some zzz’s in the tank, clownfish usually sink to the bottom of the aquarium.

They’ll sometimes sleep out in the open but commonly look for hidden spots next to decorations or plants. In rarer instances, clownfish might also sleep at the tank’s surface.

When asleep, a clownfish will still hover slightly above the ground with a normal posture. However, the fish won’t move, so it looks like it’s in a trance.

Like all fish, clownfish sleep with their eyes open because they don’t have eyelids. Thus, they need to find a dark spot to rest.

Continuous light exposure keeps them awake. This is important information because clownfish are diurnal animals (they sleep at night).

They regulate their sleeping patterns according to external cues such as light and darkness.

How do Clownfish Sleep in the Ocean?

Clownfish have virtually the same sleeping habits in the wild. They seek dark and safe spots where they lie or hover motionless to rest.

But there’s one interesting thing you might not know. In the wild, clownfish live in a symbiotic relationship with sea anemones.

When sleeping in the wild, clownfish sink to the bottom of shallow seas and seek these marine animals as a refuge.

It’s strange because anemones are dangerous and aggressive against fish approaching them.

They use their tentacles to sting and inject venom, often killing unsuspecting victims. But clownfish seem immune to these lethal stings.

Thus, clownfish can sleep peacefully between the anemone’s tentacles. The anemone provides shelter protection from other fish while the clownfish is inactive and vulnerable.

In return, the aggressive clownfish might deter other passerby’s from their sleeping spot, protecting the anemone from hungry fish.

How Long do Clownfish Sleep?

Clownfish have similar sleep requirements to most other animals. As a general rule, they need roughly 8-12 hours of sleep per day.

They’ll sleep once the lights go out, so remember to turn off the aquarium lamp in the evening. Light keeps them awake, so ensure your fish get at least 8-12 hours of darkness daily.

Like other animals, clownfish need enough sleep to stay healthy and prolong their lifespan. Insufficient sleep can lead to exhaustion and long-term problems. So, you need to ensure your fish are getting enough rest.

Note that clownfish don’t need 12 hours of continuous sleep. Clownfish might take “naps” or sleep a long time at once.

Don’t worry too much about it, though. As long as you provide the ideal sleeping conditions, your fish will do their thing and get enough rest.

When do Clownfish Sleep?

Clownfish don’t have a fixed sleep pattern. Their internal clock isn’t as complex as ours. But Clownfish are still diurnal, similar to most other animals.

This means they’re most active during the day but sleep at night. Clownfish might also sometimes nap throughout the day if your tank has hidden and shaded areas.

Of course, Nemo’s definition of “day” and “night” has nothing to do with the 24-hour cycle. Instead, this fish relies on simple environmental cues like light and darkness for going to sleep or waking up.

Even if the fish don’t have an internal clock like us, they can still get tired and sleep-deprived without daily sleep.

As I’ve mentioned, fish need at least eight hours of sleep. If the aquarium lights are on 24/7, your fish won’t get a good night’s rest.

But if you turn off the lights and put the aquarium in a dark room, you might catch your fish getting some zzz’s even in the middle of the day.

Do Clownfish Sleep on Their Side?

The normal sleeping position for clownfish is upright and hovering or floating at the bottom of the tank.

However, clownfish sometimes do weird things, such as sleeping on their side. Many aquarists have documented this peculiar behavior in their clownfish.

When this happens, the sleeping clownfish are most likely to “lie” on their side at the water’s surface.

More rarely, a sleeping clownfish might lie on its side when sleeping against corals or anemone in the tank.

The troubling part is that a fish lying sideways is usually a sign of swim bladder issues. Sometimes, fish will also lie sideways at the water surface if there’s poor gas exchange in the tank.

So, although clownfish sometimes sleep sideways and are perfectly fine, you should monitor your fish to make sure.

Do Clownfish Sleep on Sand?

Usually, clownfish sleep at the bottom of the tank, hovering above the substrate. But some clownfish also like resting on the sand.

It’s a normal sleeping behavior for them, so don’t freak out if you see this. If your fish goes to lie on the substrate but resumes its daily routine after sleep, everything is fine.

Monitor your clownfish behavior, though. A fish lying on the substrate could sometimes be a sign of infection, illness, swim bladder problems, or poor parameters like high ammonia and increased water temperature.

If your clownfish display other symptoms, their sleeping on the sand could be a sign of underlying sickness.

Health Problems in Clownfish Caused by Lack of Sleep

All animals need a minimal amount of sleep in a day. Sleep is for more than just replenishing energy.

When organisms enter sleep mode, the metabolism slows down, and the body can use the extra energy to repair cells, release hormones, and filter toxic waste. A lack of sleep can negatively impact the body and mind, even in fish.

In the best-case scenario, your clownfish will suffer from the following:

  • Lethargy due to low energy levels
  • Increased stress leading to erratic or hostile behavior
  • Lack of appetite
  • Lowered immune function

These are the first signs of sleep deprivation. If the root cause goes unchecked, these symptoms can lead to further chronic health issues.

A prolonged lack of sleep will also cause:

  • More frequent infections and illnesses due to stress and lowered immunity
  • Weight loss due to poor appetite
  • Nutritional deficiency and digestion issues (constipation, bloating)
  • Poor growth in juvenile fish
  • Shortened lifespan
  • Sudden death

Even if your fish appear to sleep in shaded areas during the day, you should still turn off the aquarium lights at night. It’s not worth taking any chances.

Sufficient darkness exposure ensures all your clownfish are well rested. A fixed light schedule will also help your fish develop a consistent sleeping routine.


Clownfish, like all animals, need sleep to maintain their health and energy levels. The ideal amount for them is 8-12 hours per day.

A lack of sleep or insufficient sleep can lead to symptoms like lethargy, poor appetite, and stress. Prolonged sleep deprivation will predispose your clownfish to health problems and early death.

Remember that clownfish are diurnal. To ensure sufficient sleep, you must provide your fish with 8-12 hours of darkness daily.

You could turn off the aquarium lights at night or keep your aquarium in a dark room.

You’ll know your clownfish are sleeping when they rest upright and motionless at the bottom of the aquarium.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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