Can Aquarium Light Be Too Bright? How much Bright is Safe?

Can Aquarium Light Be Too Bright How much Bright is Safe

Can the Aquarium light be too bright? This is one of the questions many prospective fish keepers ask and indeed it is a very important question.

Light is very important to fish and almost all aquatic animals we can keep in the aquarium, and even to those in the wild.

This is why it is important to have a lighting system for our fish tanks.

As living things, fish and all other aquarium animals react to many things, including lights, especially bright lights, and that is why many people think that a lightning system could be too bright for some fish.

Now the question is, can fish tank light be too bright for fish and other aquatic animals? we will find out in this article.

Can Aquarium Light Be Too Bright?

Every aquatic animal has its ideal level of light brightness, and when an aquarium light is brighter than it could tolerate, then the light becomes too bright and could cause problems for the animal.

Of course, the Aquarium light could be very bright.

Fish tank light being very bright is determined by many factors such as the type of fish or aquatic animal in the tank, the size of the tank, and finally, the types of plants in the aquarium.

Let me explain all these in detail so that you could comprehend them.

Factors That Determines The Brightness Of An Aquarium Lights

1. Type of animal in the tank: We all know that every animal, including aquatic animals, is different in its ways.

Some aquatic animals, especially the tropical and freshwater aquatic animals are used to brightness via sunshine.

Such types of animals are already used to bright lights and could easily adapt to any form of light’s brightness.

So, what I want you to understand is that, if you keep a very bright light for such animals, they won’t feel it much, I mean it won’t be very bright to them because they are already used to such.

On the other hand, keeping a light which freshwater tropical fish, etc sees as normal with many types of marine fish that dwells in deep seas and oceans, it could be very bright to them because they are not used to such brightness.

So, the type and nature of animals are one of the factors that determine how bright an aquarium light should be.

2. Tank size: Tank size matters a lot when it comes to fish keeping.

Every tank size has its suitable or ideal light, and it would be a mistake to keep a light that was designed for a 200-gallon tank for a 20-gallon, etc.

For instance, it is recommendable to keep 1 to 2 watts of lighting per gallon for fish-only aquariums, 2 to 5 watts per gallon for freshwater planted aquariums, and 4 to 8 watts per gallon for reef aquariums.

Again, as I explained above, you can adjust the level of the light’s brightness, depending on the type of animal you have. So try as much as possible to Buy those lighting systems that have brightness control and timer too.

3. Plants: Plants, especially live plants affect the level of light brightness in many ways.

For instance, aquarium plants will help to shade off or minimize the level of light that gets into a fish tank.

Again, it depends on the type of plants, even those with less thick leaves will have some impact too.

Effects Of Too Much Light In Aquarium

Knowing that Aquarium light could be too bright, the next thing you may be willing to ask is the effects on the fish and aquarium in general. Well here they are:

1. Algae Bloom: One thing many fish keepers don’t understand is that light is one of the things that promote algae in a fish tank.

For instance, fish tanks that are closer to where the sunlight is much normally suffer from algae Bloom.

Although algae Bloom is mainly facilitated by the type of nutrients in the water, but light is one of the helping factors.

So, too much light could feed the algae in your Aquarium, and it depletes the level of oxygen in a fish tank which could seriously affect your animals.

2. It could impact your live aquarium plants: There are 2 types of Aquarium live plants, those that grow with light and heat and those that do poorly with light.

If your live plants happen to be those that could grow very well in much light, then your bright aquarium light could boost their overall performances, but you will have problems keeping them under check or they will overgrow.

If yours are those that do poorly with much light, then you will have a problem here.

3. Stress: Bright lights could be a great source of stress for many fish and other aquatic animals.

As I explained above, it could depend on the nature of the fish, but again, how you use the light matters to the fish or the animal.

I have a full article on Aquarium lights and their usage. Check the link below.

4. It could impact your fish feeding habit and their overall health: Apart from affecting the overall health of those fish that are not very good with bright light, it could affect the eating habit of those that are even okay with bright light.

Again it depends on how you use the light.

For instance, if your fish are used to bright light at a particular hour and they feed once the light is on, changing the schedule might affect their feeding habit, etc.

How Do I Know If I Have Too Much Light In Aquarium?

There are many ways to find out if the level of light brightness you have in your fish tank is normal or much and they are:

1. The watts of the light you have: earlier in this article, I explained the normal or suitable watts of light for a gallon tank, etc, so if the watts of the light is bigger than the tank size, then it is much.

2. Behaviors of your fish: Another way to determine if a light is very bright is the behaviors of your fish and also other animals in the tank.

If your fish is stressed, not eating, or always hiding whenever the light is on, then your Aquarium light is probably very bright.

3. If there are algae, Bloom, in your tank, then it is very bright.

When I mention algae, am sure you know what that is, they are those green, brown things you could sometimes see in the water.

In fact, it comes in many colors and it is somewhat gummy and thick when it is touched.

Can Too Much Light Harm Fish?

As I explained above, too much light or bright light could affect fish in many ways such as stressing them, making them hide and depriving them of sleep and food.

Although light is very compulsory for fish of any type, the brightness should be regulated, and also usage time should be regulated too.

This is why I advise you to get the type of light that have brightness control and also a timer so that you will be able to adjust the light easily.

So, much light could have some health impacts or problems on your fish.


Aquarium lights can be bright and it is not advisable to use them on your tank unless your tank needs them, if not, go for less bright lights or those with controllers.