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How to Light an Aquarium?

7 minutes
Contrary to what you might think, too much light in an aquarium can cause something known as photoinhibition. This causes plants, algae or cyanobacteria to lose their ability to photosynthesize and stop growing.
How to Light an Aquarium?
Last update: 21 December, 2022

Fish don’t only need excellent food and a spacious tank, but they require a good lighting system to regulate their daily activities. For this reason, and to improve the quality of life of these organisms, we need to learn how to properly light an aquarium.

Although it sounds simple, there are many factors that must be taken into account when choosing the lighting for a tank. For this reason, things like the type of material the lamp is made of, the luminous capacity, or the intensity are very important when acquiring these accessories. Learn how to light your aquarium well in this article.

Is it necessary to light my aquarium?

Although it may seem like a way to show off the fish, the reality is that lighting has a deeper function. Generally, plant species need a certain amount of light to grow and thrive. In addition, fish also regulate their biological cycles according to the amount of light in their environment.

Even if the aquarium is in an area with natural light, the structure of the tank can prevent light from entering. Aside from the fish not being able to bring out their colors in the lack of light, the environment looks a little duller and darker, which could affect the health of the entire tank.

How should I light my aquarium?

The most efficient way to light an aquarium is by placing fixtures on the surface or lid. This isn’t done on a whim, as the aim is to simulate the natural lighting of the water, which is always from top to bottom. This poses a problem, because the deeper the tank, the more difficult it will be to get light to the bottom.

Manufacturers of lighting fixtures have created measurements that allow you to calculate how much light a specific fixture provides. There are currently several ways to measure light output, so only the most popular and most commonly used in aquarium environments are described in the following list:

  • Power (watts): This is a parameter that is increasingly out of use. This unit represents the amount of energy used, which used to be equal to the lighting capacity. However, with the innovation of new technologies, some lamps consume less electricity, but are more efficient in emitting light.
  • Kelvin (K): This is a measure of color that divides spectra into warm light (2200K-3500K), neutral light (3500K-5000K), and cool light (5000K-6500K). Looked at another way, warm light covers yellow-reddish tones, cold light covers blue-greenish tones and neutral light is equal to “white” light.
  • Lumen: This measurement refers to the amount of light emitted per second.
  • Lux: This term is related to the previous one, as it measures how much energy reaches a surface per second.
  • PAR (photosynthetically active radiation): This is the amount of light used for photosynthesis. This value is focused on quantifying the efficiency with which plants absorb light.

Generally speaking, the most significant values to take into account when purchasing a lamp are Lux and PAR. However, not all manufacturers provide this information, so the Kelvin and Lumen values are still used to standardize products.

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How much light does an aquarium need?

The amount of light an aquarium needs depends entirely on the number of animals, the vegetation it has and the depth of the tank. Standard values are used to calculate the light requirements of the fish as follows:

  • Low light requirement (15 lumens per liter): when there’s no real vegetation in the aquarium and only a few fish are kept.
  • Medium requirements (30 lumens per liter): the tank contains little vegetation and an average quantity of fish.
  • High light requirement (60 lumens per liter): the vegetation forms a fundamental part of the decoration and the amount of fish is very high.

In addition, remember that all aquatic life should be exposed to a maximum of 10 hours of light per day. To achieve this, there are often timer mechanisms that solve this conflict, as they can be programmed to automatically turn off the lighting.

Can I put a night light in my aquarium?

Because the amount of light per day is restricted, it’s often thought that there’s no way to have lighting in the tank at night. However, there is a type of moonlight or night light that allows you to observe your specimens in the dark. This special lighting doesn’t affect their biological cycle, as it resembles natural moonlight that doesn’t harm them in any way.

Types of lamps for aquariums

Thanks to technological advancement, there’s an excellent range of options to implement in your aquarium. However, each one presents significant differences with respect to the materials, the functions it incorporates, and durability. Thanks to this, we can classify the lamps into three main types.


These are the first lamps that were available, so nowadays their price is quite low. Most of these types of lights are color-regulated (represented in Kelvin values). In addition, the tube that composes them contains mercury gases, so if it breaks it can easily contaminate the aquarium.

The lighting effect is based on passing electric current that heats the lamp, so the light also emits heat into the tank. Although it may not seem important, this can cause certain areas of the aquarium to heat up more than others and cause problems for the fish.

On top of that, the heat itself wears out its components, making it necessary to change the fluorescents frequently.

Metal halide

As the name implies, these lamps contain metal halides that help stabilize and streamline the light output. However, this feature also causes them to be more expensive and consume more energy. This also impacts the heat they produce in the aquarium, which causes the same effect as fluorescent lights.


This is the newest technology in the aquarium world, and, thanks to their size and flexibility, LEDs have become the best option for tanks. This type of light directs the beam directly towards the aquarium, something that makes them more efficient despite producing fewer lumens.

Which is the best option?

The choice depends on the budget and commitment of the owner, because a couple of fluorescent lights may be enough, but it’s necessary to take care of the number of hours of light. LED lamps are fabulous, as several models usually have a built-in automatic shut-off mechanism that simplifies everything. In addition to this, they also exhibit night light mode, so they’re an all-in-one.

Despite this, such types of lights are some of the most expensive on the market, so they may not be within your budget. Keep in mind that the only thing you need to choose a lamp is to ensure that it’s capable of lighting your aquarium well. Weigh up each of the options well so you can decide which one suits you and your budget best.

Over-lit aquariums aren’t good

Contrary to what you might think, over-lighting an aquarium could be counterproductive, as not all fish need light in their habitat. Keeping this in mind is crucial before planning tank lighting, as each species has different requirements.

While some species tend to be active and enjoy showing off their colors, others prefer to stay in the dark to feel calm. This means that you’ll need to keep certain areas dimly lit so that some fish aren’t too stressed by too much light.

Similarly, it’s often thought that uncontrolled algae growth is due to over-lighting. However, this isn’t entirely true, as it helps them grow faster, but there are other factors such as the amount of organic matter that favor these events.

In short, light alone doesn’t encourage algae to develop, but it does drive these events when they’re already present. A well-planted and clean aquarium should not have algae overgrowth.

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Finally, remember that every aspect of an aquarium setup will impact the quality of life of the fish. Be very careful when integrating an add-on such as tank lighting, as it has more repercussions than you might think. Fish are beautiful pets that deserve all the care you can give them.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Moheimani, N. R., Borowitzka, M. A., Isdepsky, A., & Sing, S. F. (2013). Standard methods for measuring growth of algae and their composition. In Algae for biofuels and energy (pp. 265-284). Springer, Dordrecht.
  • Riddle, D. (2012). Aquarium Lighting: Moonlight-A Concise Review of Its Spectrum, Intensity, Photoperiod, and Relationship to Coral and Fish Spawning. Advanced Aquarist Feature Article.
  • Rhyne, A. L., & Tlusty, M. F. (2012). Trends in the marine aquarium trade: the influence of global economics and technology. Aquaculture, Aquariums, Conservation & Legislation 5: 99-102.
  • Cheng, J. H., Lin, H. H., & Yen, C. C. (2019, July). The Spotlight Effects of LED Lighting Design for Deep Aquarium Tanks. In 2019 IEEE 2nd International Conference on Knowledge Innovation and Invention (ICKII) (pp. 358-361). IEEE.
  • Tullock, J. H. (2007). Freshwater Aquarium Models. John Wiley & Sons.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.