Can Fish See in the Dark?

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Ever wondered what your fish are up to when the lights go out? Some of you may have imagined them taking a nap or perhaps quietly swimming around. But can fish see in the dark or do they just float aimlessly?

Well, the answer isn’t as straightforward as you might think.

can fish see in the dark

Can fish see in the dark?

530 million years of evolution have shaped fish vision to adapt to various lighting conditions. Similar to the human eye, fish have rod cells for seeing in low light and cone cells for detecting colors and finer details.

However, the ratio of rod cells to cone cells in fish varies depending on the species and their environment.

Betta fish, for example, can see in dim light, but it may not be as sharp or clear as their vision in bright light.

Bettas also have a layer of tissue behind the retina called the tapetum lucidum. This layer acts like a mirror, reflecting light back into the eye and increasing their visual sensitivity.

Goldfish, on the other hand, don’t have the same level of visual acuity, which is why they also rely on their sense of smell and lateral line system to navigate and detect movements.

Furthermore, many deep-sea fish have developed special adaptations to see in near-complete darkness and many of them even have bioluminescent organs that produce their own light.

In other words, they glow!

We won’t go into detail about all the different types of fish here, but hopefully, you get the idea.

What do fish do when it’s dark?

Not all fish hit the hay and call it a night when you turn off the lights in an aquarium,

For some nocturnal fish, such as certain species of catfish and tetras, a dimly lit or dark tank is a sign to start becoming more active. These fish have adapted to thrive in low-light conditions and often use this time to hunt and find food.

Diurnal (or day-active) fish tend to do the opposite and will typically become less active and seek shelter during the nighttime.

Are fish afraid of the dark?

Although it’s difficult to determine exactly how fish perceive darkness, it’s believed that they’re not necessarily afraid of the dark in the same way humans might be.

RELATED: Do Fish Need Light at Night?

This is probably because (again) many fish have adapted to low-light or even completely dark environments, while others rely on their other senses as a substitute for night vision.

They can, however, be more sensitive to sudden changes in light levels.

Can fish be fed in the dark?

When it comes to nocturnal fish species, feeding in the dark isn’t only possible, but it may actually be preferred.

Yet, most common aquarium fish should be fed primarily during daylight hours as feeding them in the dark could potentially throw off their normal feeding patterns and disrupt their natural behavior.

If you have a mixture of diurnal and nocturnal fish in your tank, it’s important to adjust your feeding schedule appropriately.

In summary

While some fish have developed advanced visual capabilities that allow them to see better in low-light conditions, others have adapted to rely on other senses to see in the dark.

The extent of these adaptations will greatly vary depending on the specific breed and natural habitats.

About the author

Li-ran B.

Li-ran has been taking care of fish since he was a young kid and considers himself a self-proclaimed aquatic hobbyist at heart. What started as a simple childhood curiosity quickly turned into a full-fledged passion. Currently, his new obsessions are nano aquariums and glowing fish tank decorations.