Home Fish Science Do Fish Need Sunlight? (Complete Explanation)

Do Fish Need Sunlight? (Complete Explanation)

by gvald

Are you starting out in the exciting world of aquarium keeping? You are changing your tank and you only have to choose the lighting ? Are you looking to recreate an atmosphere? We will detail the different lighting options available in an aquarium to help you choose the right lighting for your setup.


Do fish need light?

Of course, they do! Like most animals, fish need light to stay healthy. Light is part of the fish’s internal clock and affects fish rest, appetite and behavior. It can also affect the color of the fish, which will become duller if light is lacking.


Most aquariums come with a lighting gallery. If you do not have one, aquarium lighting can be purchased and installed separately (see a selection here).


The most common lighting is in the form of tubes (T8 fluorescent tubes and more recently the smaller but more efficient T5). More recently, there are LED lights (for ‘Light Emitting Diode’ in English), much more expensive but much less energy consuming, whose intensity can be adjusted, which last longer and which generate very little heat compared to fluorescent tubes.


Is daylight enough?

Yes, natural light can be sufficient, but you should avoid placing your aquarium directly behind a window. This will encourage algae growth and – more seriously – cause the aquarium temperature to rise excessively in summer. Note that a lighting gallery will be necessary in any case if you wish to grow plants.


Can my fish have too much light?

Yes, too much light can be as bad as none at all. It is therefore recommended leaving the aquarium lighting on for a maximum of 8 to 12 hours per day and to have a lighting level that is adapted to your tank (an overabundance of light can also promote algae and stress the fish).


How to properly light your aquarium?

Poor lighting (frequency, power, exposure, …) can cause many problems such as algae growth in the aquarium. Therefore, it is important to adjust the light level and to use the lighting according to some basic principles. There are a few basics to know:


First, it is not necessary to light in the morning. Prefer the beginning of the afternoon to turn on your lamps. In order to better organize yourself, you can buy a timer that will turn the lights on and off independently. There are also lamps that turn on and off progressively with a natural effect of sunrise and sunset so as not to disturb your population. (For about thirty euros on the internet).


Attention: It is important that the lighting time is not superior to 12 hours in order not to disturb the fish cycle.


Then, you must choose your lighting according to the desired heat and the length/depth of your tank. Here are some useful data:

Prefer neon lights close to blue, red and orange with a temperature close to 6000°K

Powerful neon lights above 40L/watt (to be adapted according to the size of the tank)

The color rendering index (CRI) must be close to 90


Should the aquarium light be turned off at night?

Recreating the true day and night cycle is best for the health of the fish and plants.


Continuous lighting promotes the development of algae to the detriment of plants and, above all, tires the fish, which also need to rest in the dark.

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