Can Aquarium Fish See At Night/Dark?

If you have a pet fish at home, you may have wondered if your little aquatic friend can see in the dark or not.

As fish do not have eyelids, they cannot close their eyes at nighttime or while sleeping, so it is hard to tell whether they can see in the dark or not.

Fret not; today, we will solve this mystery for you. Keep reading this guide to find out answers to the age-old question: Can fish see in the dark/night?

Can Fish See In The Dark?

Yes, contrary to popular opinion, fish can see in the dark, but there is a catch to it.

Most common aquarium fish like goldfish, guppy fish, betta fish, cory fish, etc., can somewhat see in the dark, but it is not with their eyes.

These fish have some level of night vision, even in the dark.

If you turn off all the aquarium lights and the room is also dark, these fish may still be able to see a little despite the darkness.

The interesting part, however, is that fish do not see in the dark with their eyes.

Instead, they make use of their pressure-sensitive organs called neuromasts, which enable them to see in the dark.

These organs are present in lines along the side of their bodies, and they can sense other fish through pressure changes in the water.

Neuromasts help the fish detect any sort of movement in the tank, whether it is changing pressure or vibration in the water in the dark.

The fish can sense different objects with the help of neuromasts and protect themselves from any potential threats.

Swimming in The Dark

When it comes to swimming in the dark, most fish can easily do that. All they have to do is send sensory signals around.

This helps them stay safe in the fish tank as these sensory signals warn other fish of their presence.

These signals are sent from their neuromast organs through the water waves, which can be easily detected by other fish.

Despite their ability to send and sense signals in the dark, fish do not prefer swimming in the dark so much.

Since they can communicate with their fellow fish in the aquarium tank by sending signals in the water, swimming is limited. They move around a little, if necessary.

Sleeping and Nap Times For Fish

Ever wondered whether your pet fish go to sleep or not? You must have heard from fish veterans to keep the tank lights off at night.

Doing so offers a fish the same environment as its natural habitat where they are restricted to receiving sunlight during the day only.

So, this brings us back to our original question, and the answer is yes. Yes, a fish is prone to get tired and sleep like most living species.

However, it is not necessary for a fish to have a fixed time for sleeping.

Ever noticed your fish randomly hovering in the water without fluttering its fin. It may appear that the fish is lost in its own world.

Your fish is, in fact, taking a nap when it appears to seem lost in a trance.

However, do not expect your fish to have its eyes closed while it’s sleeping, as fish do not have eyelids.

It is the absence of eyelids that misleads people into believing that fish do not sleep. But fish do get tired and rest up to recharge themselves.

Moreover, keep in mind that not all the fish in the tank have the same sleeping pattern.

They all sleep at different times, and it doesn’t always require them to keep the lights off.

Is Darkness Essential for Your Aquarium Fish?

As we know that fish use neuromasts to sense things in the dark, you may wonder if it is even necessary to put them in that spot or not. The answer to the question is ‘Yes.’

It is necessary for fish to stay in the dark due to several reasons.

First of all, like all species, fish also need to maintain a disciplined routine in order to function properly.

They cannot have the same conditions 24/7, or else it will create problems for them. Fish require both light and darkness in the right amount.

Maintaining both a light and dark atmosphere for your fish in their aquarium is crucial for their physical needs.

Fish also need to maintain light and dark time periods so they can rest and recharge themselves after swimming, playing around, and eating food every day.

A 12-hour sleep or darkness cycle is appropriate for all aquarium fish so they can rest or sleep or just take some time off.

Your fish may not follow the same sleeping pattern of day and night, but they do need time to rest and fuel up energy.

Also read: Do Betta Fish Need Darkness to Sleep?

Color Detection Underwater In The Dark

There is a whole science behind how colors appear underwater. Whether a color is clearly visible underwater in the dark is dependent on its wavelength and absorption levels.

All colors have varying wavelengths and absorption levels that affect their visibility underwater.

For instance, lights in red and orange tones have an absorption level of 30 meters underwater.

As discussed earlier that fish can indeed see in the dark. This means that they can see and detect different colors too.

It also depends on the species of fish, as some fish have laser-sharp vision. No matter if it’s day or night, some fish have perfect vision and can see clearly in the dark.

These fish can detect different colors, even those with ultra-violet frequencies.

These fish have a special chemical coating on their eyes that helps clear their vision and enables them to detect different color shades like grey, light, and dark tones.

In addition to this, the quality of the water also helps with the visibility of different colors underwater.

If your fish tank water is cloudy or dirty, it will become difficult for fish to detect colors or even far-placed objects in the tank.

If there are algae, bacteria, or other contaminants in the water, it further hinders the vision of the fish and makes it difficult for them to detect different colors and lights.

This is why you need to regularly clean your aquarium to ensure the water is free from pollutants and your fish can easily see and swim around the tank without any hassle.

Is There Any Color of Light That Fish Cannot See?

Fish are not color blind, and most fish can see almost all colors underwater, depending on their absorption levels and wavelengths.

However, the case differs for some fish with different anatomies.

Most fish have their eyes located in the center except for a few that have eyes pointing out opposite sides of their head.

Their eyes are round and bulging in shape, and they come with their own drawbacks.

First of all, as the eyes are placed opposite to each other, these fish do not have binocular vision.

Due to their eye placement, they have this semi-blind spot in their vision that hinders them from clearly seeing things that are right in front of them.

Besides this, most fish have poor far-sighted vision, while their nearsightedness may be excellent. This factor also affects their ability to detect colors.

The nearer the color light or object is to them, the better they can see those.

When it comes to light sensitivity, most aquarium fish prefer blue and cooler tones. This is why it is recommended to install blue lights in the aquarium, especially during the night.

Fish and Red Color

Contrary to popular opinion, fish are not drawn to the color red. Yes, they do find it attractive, but that has more to do with taste rather than aesthetics.

Fish find red color attractive because of the taste of red-colored food.

For example, red blood worms are a staple favorite of fish not because of the color but their taste.

Even without tasting the food item, fish can tell that this red color food is something that would pique their interest.     

So, don’t be surprised the next time you see your fish swimming towards a red-colored object underwater, be it food or just a fake plant.

Tips To Help Protect Your Fish’s Vision

In order to save your fish’s vision, you need to protect it by giving them the right kind of food to eat.

The healthier your fish is, the better their vision.

Another significant factor that would play a pivotal role in keeping your fish’s vision right and safe is the amount of light the aquarium is getting. Make sure that your aquarium gets at least twelve hours of light.

However, also take note that darkness is also as important for a fish’s eyes.

So, what you need to do is to find a perfect balance of durations your aquarium must have, light and dark.

For example, the best balance is to keep the aquarium lit for twelve hours and switch the lights off for another twelve.

This will trigger the perfect balance, and your fish’s vision will also remain perfectly fine.

By achieving this balance, you will be helping your fish to keep their sight sharp and accurate.

Usually, the fish do not have an issue with their vision; however, as they grow older and catch diseases, along with other conditions and weaknesses, the fish do tend to get weak eyesight.

The Bottom Line

We hope you enjoyed reading this guide on ‘Can fish see at nigh/dark?’ and it helped answer all your concerns regarding the topic.

Please do refer to the tips mentioned above if you see your fish struggling with their routine.

If you found this blog helpful, do share it with your friends and loved ones and help spread the word.

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