Can Oscar fish see in the dark? Do they sleep at night?


Share on facebook
Share on twitter
Share on pinterest
Share on whatsapp
Can Oscar fish see in the dark

From small animals to giant blue whales, all animals need rest. And although rest and sleep are necessary for the survival of virtually all species, dozing can look quite drastic for individual animals. So are the Oscars sleeping? And can Oscar fish see in the dark?

In this blog, I will tell you everything there is to know about the sleeping routine of oscar fish or if they could see in the dark.

Things are going to get interesting.

Does Oscar Fish sleep and can oscar fish see in the dark?

Yes, Oscar fish do sleep. They depart to their favorite corners at the bottom of the aquarium and call it a night. They have sleep cycles just like us. And their bodies also produce hormones that regulate their sleep patterns and calibrate their internal clocks.

Fish do not sleep like humans for many reasons. But they don’t have eyelids, to begin with. That’s why they can’t close their eyes. That is also why Oscar fish can’t see in the dark.

However, when night creeps in, Oscars, like all fish, become less responsive. Their heart rate and metabolism decrease.

Scientists have not yet been able to study what happens inside the fish brain during sleep.

So we have to take an alternative route to study Oscar fish sleep – his behavior.

Below are four criteria that prove that Oscar fish are sleeping after all:

  • A typical resting position in a shelter
  • Inactivity for an extended period
  • Alternating with activity in a 24-hour cycle
  • High thresholds of excitement

So, based on these four criteria, we can conclude that the Oscar fish are sleeping.
There are quite a few differences between how Oscar fish and humans sleep. The first is that Oscar fish don’t close their eyes when they sleep because they don’t have eyelids. That is why they can’t see in the dark too. Furthermore, areas of the brain, specifically in the neocortex, become passive when people sleep. But Oscar fish don’t have a neocortex.

Whatever little we know about the sleep cycle of fish is thanks to the zebrafish.

Zebrafish’s translucent skin means you can get up close to their brain cells and see what’s going on inside with an advanced microscope.

Read Also: What is The Best Temp For Oscar Fish?

How does Oscar Fish sleep?

Sleeping habits across and within different fish species are as varied as they come. Some Oscar fish retreat to a corner at the bottom, others prefer to sleep in caves. Some fish even like to sleep on top or in the air – so don’t be surprised!

No offense, but oscar fish still need oxygen to exist. And they get it when water passes against their gills, which need a certain level of movement. So even when you are sleeping, you will notice that the fins move now and then to create water currents near them.

Why does Oscar Fish sleep?

Can Oscar fish see in the dark

Oscars sleep for the same reason you and I sleep! The reasons why Oscar fish sleep can generally be divided into two categories: the restorative sleep hypothesis and the adaptive sleep hypothesis.

Let’s take a quick look!

Hypotheses of restorative sleep
The restorative theory of sleep states that a being sleeps to help the body recover. During sleep, the body repairs itself, processes memories and new information, and, last but not least, strengthens the immune system.
Adaptive sleep hypotheses
On the other hand, according to adaptive theories of sleep, a being sleeps to better adapt to its environment. For example, sleep helps a creature avoid dangerous scenarios, such as an encounter with a predator.

Can Oscar Fish see in the dark?

No, as interesting as it would be, the Oscars can’t see in the dark. However, fish living in deep seas and oceans have evolved to have highly sensitive eyes capable of seeing a wide range of color shades even in near darkness!

How can your oscar fish get enough sleep?

The best and most important way to ensure your oscar gets enough sleep is to turn on the tank light on a timer to mimic a day and night routine. Also, make sure you add enough cover to the aquarium to keep your Oscar fish comfortable at night.


No, they cannot see in the dark. But Yes, Oscar fish sleep. They don’t sleep as we do, but they sure like to hide in their cozy place at night—whether it’s a cave, the corner of a tank, or the air—and rest.

Although they don’t close their eyes because they don’t have eyelids, they lie still, reducing their heart and respiratory functions and secreting a sleep-inducing hormone!