Do Aquarium Lights Stress Fish?

Do Aquarium Lights Stress Fish?

We all know that fish of all types need lights in the aquarium and it is very important for them, but the question many ask is, do aquarium lights stress fish?

You might be wondering that if lights are very important to fish, then how would it stress them as popularly believed by many Aquarists? you will learn all about that in this article.

Aquarium lights will stress fish if it is not properly used.

The fact is that everything has its advantages and disadvantages, and the disadvantages come when it is not properly put into use.

Even though light is very necessary for aquarium fish, it could stress them too.

You will agree with me on this if you keep a very bright light for your fish tank, you must have noticed that your fish will always be frantic and very afraid when you switch it on all of a sudden.

When this happens, you will see them dive into the substrates, caves, and in fact on anything that could hide them because the sudden bright light is scary and once a fish behaves that way, it will become stressed.

Unlike human beings and many other animals whose eyes are made to control or deal with an excessive amount of light with the help of the retina and eyelids, fish eyes are different.

Fish do have retinas but it takes more time for their eyes to control the amount of light that is seen.

It takes up to 30 minutes for their eyes to become used to a light when it is flashed or switched ON all of a sudden and it takes up to an hour for the same eyes to blend in with darkness when the light is OFF.

Fish eyes are not much different from those of other vertebrates, including humans.

Our eyes have a cornea, an iris, a lens, a pupil, and a retina.

The latter contains rods that allow us to see in dim light and cones that perceive colors; while mammals (like us) have two types of cones, fish have three—one for each of the colors red, green, and blue. These connect to nerve cells which transmit images to the brain, and the optic lobe is the largest part of the fish’s brain.

This is to say that once a light, especially a bright light is shown on fish, it does not only affect the eyes but the whole body and it is very stressful for them.

Do Fish Like Light In Their Tank?

Fish do not only like having light in their tanks, but they also need it.

Despite that, they like having light and it must be provided for them but only the right type of light and also knowing how to use it so that it won’t turn from good to bad by stressing them.

How To Use Aquarium Lights

Now you know that lights could act as an agent of stress for your fish if not put to proper use, the question you may be willing to ask next is how to use Aquarium lights the right way.

Before switching on an aquarium light, first of all, switch ON the room light or any light that is very far from the fish and leave it on for a few minutes, so that the fish could be used to the light, then switch ON the aquarium light.

The motive here is just to make the fish’s eyes get used to the distance light so that the fish won’t have to react frightfully when the main light ( Aquarium light) is switched on.

Since fish also reacts negatively when the light is switched off, it is advisable to still leave the room light on when you put off the aquarium light and then turn off the room light later so that they could get used to very dim light and won’t have to react when total darkness creeps in.

Can Too Much Light Stress Fish?

Apart from switching on the aquarium light or flashing light on fish all of a sudden, another thing that could stress fish is too much light or very bright light.

You can use either Florescent light, incandescent, or LED light on your aquarium but any of the lights that you choose must not be very bright, in fact, I even advise people to get a type of light that is somewhat dim because too much light can stress your fish as it takes time for their eyes to control the amount of light they see.

So, too much light will stress your fish, so avoid it in your fish tank.


Aquarium light is good, and it could also stress your fish too, so know how you operate it and also avoid very bright light because it will help in stressing your fish.


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