Do Fish Like the Dark?

In their natural environment, most fish species experience hours of light and darkness, as caused by the rising and setting of the sun. But in an aquarium environment, the hours of light and dark is in the hands of the tank keeper. Indeed, you can keep the lights on or turn it off for as short or as long as you want!

Do fish like the dark? Yes, they do! Fish will thrive in a tank environment where there are specific periods of near-complete to complete darkness. It is because they, too, need sufficient hours of sleep for good health.

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Read on and find out the number of hours fish need darkness and the things you can do to ensure that they get it. You will require a few supplies including LED lights and a timer for this purpose.

Determining The Number Of Hours Of Darkness

Every fish species have specific light requirements and, thus, it’s essential to do your research about it. But in general, most fish species require about 12 hours of light a day and 12 hours of nighttime conditions. It means the aquarium lights must be turned off for 12 hours at night, although blue lights are also acceptable.

But that’s a general recommendation! You have to consider several factors in determining the actual number of hours when the lights are turned off.

  1. The fish species in the tank since they will be affected by too much and too little light
  2. The types and amount of plants in the tank
  3. The location of the lighting, such as top or side
  4. Where the tank is located in the room, such as near a window or under bright overhead lights

For example, a tropical aquarium with plants should have nighttime conditions for 12 hours every day. A cold water aquarium with cold water fish and plants should ideally have 16 hours of darkness. Otherwise, the water temperature can increase, and flora and fauna will become unhealthy over time.

Controlling The Light And Dark Cycle

But you can’t always turn off the lights, such as when you’re on an out-of-town trip or remember to do so every night. Your fish can suffer from poor health, or the algae can bloom due to the overexposure to light over several days. You must then have a way of controlling the light and dark cycle.

It is where timers like the Current USA Single Ramp Timer for Aquarium come in handy! An aquarium timer is easy to use, too, since you just set the specific times when the lights should be turned on and off. The consistency of the cycle will mimic the fish’s natural environment and contribute to their excellent health.

Do Fish Like the Dark?


To conclude, most fish species don’t have eyelids, and, as such, they are vulnerable to 24/7 light conditions. They need near-total, if not total, darkness to allow them to sleep, just as we do. They will benefit from a dimmer, too, which gradually dim and brighten the lights to mimic the transitions of dusk and dawn.