Do Fish Tanks Need Light? Can I Turn Them Off At Night?

You’ve got yourself a new fish tank and you are all excited. But something is troubling you. Does my fish tank need lighting?

Let me answer it as clearly as possible:

Your fish tank does need lighting and you can turn them off at night. However, the amount depends on the type of fish and the environment you want to create.

The answer might seem simple but there are several nuances to this subject. From the type of fish you plan on keeping to the type of plants you want, lighting plays a crucial role. How crucial? Read on to find out.

Why Fish Tanks Need Lighting?

Ask any seasoned fish owner and he will tell you this:

Fish are at their peak health when the tank resembles their natural habitat.

This is not a surprise. Fish, at the end of the day, are wild creatures. They need a habitat that provides them with proper nourishment as well as serves their primal instincts. So, before purchasing any fish carefully consider these questions:

  • What species is this?
  • What kind of habitat do they live in?
  • How do I make the fish tank mimic their natural habitat?

You must research these questions and carefully consider your options.

The good news is, it is not anything like rocket science. Just pay attention to a couple of key points and you’ll be good to go.

Firstly, you need to consider is the type of fish. When it comes to lighting, fish can be broadly classified into two types:

  • Fish who are used to bright light
  • Fish who live in dark places

The lighting requirements of your fish tank will depend on the type of fish you keep.

For fish who are accustomed to bright light, you need to properly illuminate your aquarium. These fish have a pretty regulated body clock. When I say body clock I mean their bodies respond to the amount of light. Ample light is indicative of daytime which makes the fish active. As soon as the lights are dimmed, the fish go into sleep mode.

On the other hand, fish who live in depths of the ocean or murky lakes aren’t accustomed to bright light. In this case, if the tank has too much lighting, the fish will get disturbed which will harm their health.

Secondly, the plants you want to keep also make a difference when it comes to lighting. Some plants need ample light for Photosynthesis while others can grow without much light. As a result, when it comes to plants, there is no concrete answer and everything depends on the individual species.

Fish Tank Needs Lights (Video)

Different Types of Lighting

Now that you know lighting is necessary, let’s figure what type of lighting you need.

Generally, lighting is of the following types:


Fluorescent is, perhaps, the most commonly used lighting type. These lights are suitable for almost all of the freshwater fish and plants. Ample, bright light and inexpensive to boot are some of the qualities that make Fluorescent lights suitable for most occasions.

T-5 HO Fluorescent

T-5 HO is a type of fluorescent that produces more light than regular fluorescents. The term ‘HO’ in the name signifies High Output. T-5 produces almost twice as much light and is thus geared towards people who own large tanks and require a stronger light source for better illumination.

One side effect of T-5 HO is that it produces more heat. So, you should be careful and should carefully monitor the temperature of the tank when using T-5 HO.

L.E.D (Light Emitting Diode)

Amongst the types of lights discussed above, LED, in my opinion, is the best one. A Light Emitting Diode boasts several advantages over the Fluorescent and T-5 HO. First and Foremost, it is cheaper to operate. Secondly, unlike Fluorescent, it lasts a long time without any change to the amount and color of light.

These are the most common types of lights used in aquariums. Not all of them are suited for every tank. Choose the type of light after considering the type of fish and plants you plan on keeping.

Common Lighting Requirements

If you have been paying attention, you will have noticed a pattern:

The type of light needed is subjective.

Similarly, the amount of light you need depends greatly on the type of fish and plants you keep. On average, most fish species need 10-12 hours of light. This number varies depending on the following factors:

  • The number and type of plants
  • Light requirements of individual fish species
  • The amount of ambient light already available

As a thumb rule remember this:

The more the plants, the more light will be required.

The Effects of Lighting on Aquatic Plants

Aquatic plants aren’t much different than surface ones. Both of them require nutrients and a healthy amount of light to grow. More specifically, light is needed for photosynthesis.

For the uninitiated:

Photosynthesis is a process by which plants take in Carbon Dioxide and Light to produce food and Oxygen.

So, the more the light, the more Photosynthesis and hence more food. This is the reason why you need to have sufficient light in your fish tank. Without it, the plants will start to lose their vitality and will ultimately die.

The Effects of Lighting on Different Fish

Just like plants, different fish also need different amounts of light.

Light is essential for the proper growth of fish. The amount of light entering the tank regulates the internal body clocks of the fish. With increased light, fish wake up and become active. Similarly, when it gets dark, the internal clock kicks in and fish go to sleep.

On the other hand, If there is too little light, most fish will lose their appetite and their colors will appear dull. If not resolved, the situation can prove fatal.

The best you can do in this regard is to try to mimic the lighting conditions of your fish’s natural habitat. Get as close as you can!

The Side Effects of Too Much Light

There is a Chinese saying:

Wu Ji Bi Fan.

It loosely translates to:

Too much of anything is bad.

This is exactly how you should view lighting. Too much lighting is pretty bad for not only the fish but also your fish tank.

In the case of fish, too much light can disturb their metabolism. Not only that fish can also become stressed which can prove to be fatal.

Similarly, your fish tank as a whole also suffers when there is too much light. Algae grow at an accelerated pace under increased lighting. An increase in the amount of Algae not only pollutes the tank but also reduces the amount of Oxygen when the Algae eventually dies.

To tackle this issue, it is crucial to regulate the amount of light your fish tank gets.

Regulating Light

Too much or too little light can spell doom for a fish owner. The loss of fish and the ever-increasing risk of Algae overgrowth are troubling matters. Keeping this in mind, it is pretty important to regulate the lighting.

Following are two simple ways that you can do this:

  • Buy an electronic timer
  • Set an alarm to turn the lights on and off at the same time each day

The latter point is self-explanatory. The first point, however, requires a little explanation.

An electronic timer is a device that regulates the lighting by turning the lights on and off at the same time every day. You just set the time you want and it takes care of the rest.

This is pretty much all you need to know about lighting for your fish tank. If I were to summarize this discussion in a few sentences, It would be:

Research before purchasing any lighting and don’t use too much. Plus, use a timer to regulate it.

Frequently Asked Questions

Are LED lights good for fish?

LED lights are quite good for fish. These lights use far less electricity than other lights, say, Fluorescent. Plus, they also produce less heat and can last for a long time without suffering from the color shift.

Can fish see in the dark in a fish tank?

The question of whether fish can see in the dark is highly subjective. There are fish species which can see in the dark but these are mostly deep-sea fish. Fish taken from ponds and freshwater lakes can’t see in the dark.

Do fish like aquarium lights?

Fish need aquarium lights. The absence of light can have adverse effects on their health and overall appearance. If there is not enough light, most fish lose their appetite and their colors become dull.

Can LED lights cause more algae in an aquarium?

No LED lights specifically don’t cause more Algae. The growth of Algae depends on a couple of factors:

  • The competition for light
  • The amount of light

If there are no aquatic plants, Algae will have no competition and its growth will be accelerated.

On the other hand, if there is more light than needed than Algae is going to grow at an increased rate.

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