Can I Cover My Fish Tank With A Towel At Night?

Lights at night in the vicinity of your favorite pet zone, the fish tank, can create a stressful environment and hinder their ability to sleep. It is important to realize that fish can navigate through plants and between rocks, even when they can’t see clearly. However, they may not be that smart in recognizing large objects in a dark environment. So, it’s not wise to make the ambiance fully dark like a ghost town. You may use a low-intensity blue LED “moon” light, giving them a calming effect for a better slumber.

This article explains some incredibly simple methods to improve the living conditions for fish at night.

Should You Cover Your Fish Tank at Night?

When you cover your fish tank at night, say with a towel, it surely darkens the enclosure, but it also runs a potential risk of suffocation due to a lack of oxygen that could endanger your aquatic species. I’m sure you do not want to put them into perpetual sleep, even unintentionally.

Imagine covering yourself entirely under a blanket. Besides the darkness underneath the blanket, just the feeling of breathlessness is scary, isn’t it? Similarly, those mute water creatures also have a frightening experience when their dwelling is pitch dark when covered fully.

It goes without saying, that most fish tank enthusiasts essentially equip these days with air pumps and plants to oxygenate the aquatic habitat. So, the fish can always breathe easily and sleep well at night.

But we need to examine if the light affects the sleep quality of the fish. Does lighting or no lighting at night disrupt their sleep pattern? Can they distinguish between day and night depending on the lighting intensity? How do you know if a fish is sleeping?

TIP: Most fishes don’t have eyelids. They enter a restful state while they are sleeping, which is characterized by stillness, and decreased respiratory and metabolic rates.

When their surrounding is devoid of sound and light, most of the fish variety tend to relax, irrespective of whether it is day or night. Of course, there are some varieties that are hyperactive and move across from one end to the other. And by night, when we switch off the lights, they all adapt to their silent surrounding at sleep time or night time.

Did you know a fish will develop difficulties if it spends too much time in the dark, including becoming inactive, color fading, and disruptions to its regular activities? On the other side, too much light prevents them from getting the necessary amount of sleep to maintain their health.

However, once in a tank or aquarium, fish may find it challenging to distinguish between day and night without the aid of additional, specialized tank illumination.

Methods for Better Aqua Environment

Like us, fish live in a world with light during the day and darkness at night. This contrast in light helps signal to their senses whether they should be awake or relaxed. There may not be a universal method that applies to all types of fish.

Goldfish sleep better when completely dark and quiet, irrespective of the time, whereas others can sleep only at night. The majority of aquarium fish are diurnal, or active during the day and sleep at night.

While some species spend the day sleeping in a cave or nook, others are nocturnal and roam at night. This category includes loaches, some knife fish, and some catfish and plecostomus species, among others.

Nevertheless, the fact remains that high-intensity glare is best avoided at nighttime. Here are some recommendations to provide a conducive environment for the fish to sleep comfortably:

  1. Use a small light over the fish tank, just to give an aesthetic effect, if you really need to turn on your light at night. You may use something to block the light to minimize the intensity of the brightness.
  2. For fish, many reef tank owners use floating plants to create a little cave or hide. If you can get enough light in there, like from a desk lamp or small nightstand light, then it won’t affect the fish too much.
  3. If you can turn off your room lights and then dim the aquarium so that they don’t get startled by it that would be ideal.
  4. Try to find ways to cover up the surrounding lights with things like plants or some pleasant wallpaper. Some fish get hostile to certain colors, so be mindful while selecting wallpaper for your tank. Ideally, the green or blue color is considered pleasant with sceneries of water plants.
  5. A darkened environment can keep fish in their light cycle. It was one of the best things I did for my goldfish. But the condition may vary with the variety of fish you have in the tank.
  6. Setting your aquarium light on a timer will provide your fish with a consistent day and night pattern and ensure they get enough sleep.
  7. Provide plenty of enclosure in your aquarium as well, so that all of your fish can feel safe while resting.
  8. Turn off the lights from digital devices and the nightstand lamp if it is near your fish tank. They are a bright light and might suppress the sleep-promoting hormone melatonin.


For various reasons, leaving the lights off for the duration of the night is typically the best option for your fish. If you must cover your tank at night, it is best not to douse the lights completely.

But you don’t need to keep them on all night long. Instead, dim the room and create a calm atmosphere to ensure a peaceful night’s sleep for your fish. Make sure that they still have plenty of room to relocate if they feel threatened or want to engage in another activity.


Light pollution makes fish more courageous — ScienceDaily

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