Many Betta fish owners wants to know if bettas do sleep or not. Of course,, that’s the next question that pops up when you see your betta lying motionless with eyes wide open, and you think it is dead, then suddenly you find it swimming again.
So, you wonder do betta fish sleep? Certainly! Betta fish do sleep. Just like any other animal, sleep is important to stay healthy. And, if you wonder why their eyes are always open, then it is because they do not have eyelid which is typical of fish. As a result, your betta is most likely to sleep when the lights are off. Old or exhausted bettas, however, are exceptions as they can sleep even with the lights on.
You can help your betta maintain a good sleep cycle. Of course, now you know they tend to sleep with the lights off. Hence, this page covers all you need to know about bettas sleeping.
Betta fish come from areas of Asia primarily controlled by wet and dry seasons instead of four distinct seasons. This makes the temperatures very consistent for much of the year, as is the length of the day. In a betta’s natural habitat, a day will normally last for 12 hours while the night will also last for 12 hours.
In a perfect world, all captive bettas would have perfectly timed 12 hour days and 12 hour nights. However, since most tanks cannot provide enough fertilizers and CO2 to match the high levels of light, massive algae growth can occur. While it is not ideal, your betta will still thrive with 6-8-hour days and longer dark periods, though it is unlikely that your fish will sleep for that full time period.
Even if your betta is provided with a longer potential sleeping time, this doesn’t necessarily mean they will use it. Betta fish are highly intelligent and need frequent stimulation, so they will still swim around their tanks in the darkness, even when they can’t see.
The day/night cycle is incredibly important for the fish’s overall wellbeing, and without a consistent one, they can fall ill. It is much more important for the schedule to be consistent than to be “perfect”. It is better to have a 6 hour light cycle that turns on and off at the same time every day than it is to have a 12 hour day/night cycle that varies day by day.
How Do Fish Sleep?
One question you may have is; how do fish sleep? Fish need to constantly move in order to push water through their gills to breathe, so how do they sleep, swim, and see in the dark all at the same time? Unlike most other animals, fish are capable of resting/sleeping with only half of their brain at one time.
This helps keep them awake and alert enough to avoid danger and obstacles while sleeping. It also allows them to gently hover/swim in one position while sleeping in order to stay alive. They alternate the part of the brain they are resting multiple times per night.
Humans are not capable of doing this, as they never had the evolutionary need to. Betta fish are not capable of building structures and safe places that they can sleep in, so they are forced to always sleep in relatively open areas where predators are always present.
The only way for them to stay alive was to stay alert, even when sleeping. Therefore, they developed the unusual ability to sleep with only half of their brain at a time. However, this does not explain how they are able to see a predator coming in the dark, especially with half of their brain turned off.
Sight Without Light
In terms of a betta being able to see without light, they cannot. Just like our eyes, they need some light in order to see, and if the moon is dim or they are in a dark room, they will not be able to make anything out. During the day, however, they have incredible sight for a fish, and are able to track objects and pinpoint their location, even without colored depth perception.
However, this wonderful sense of theirs is useless at night. They would also not be able to smell, hear, or taste a predator approaching in cases, and if the predator got close enough to touch them, it would already be too late. So, what sense do they use?
Betta fish, and several other fish have what is referred to as a “sixth sense”. They have a lateral line going from their head to their tail, which can sometimes be seen. This line houses pressure sensors, which act as a betta’s eyes in the dark.
These pressure sensors are capable of detecting very faint vibrations and movement in bodies of water, and they give betta’s an understanding of the still and moving objects around them. This is what allows them to evade a predator in pitch-black darkness while still avoiding any obstacles around them, even without the use of their eyes or other senses.
Aquarium night light settings, which are dim lights that are normally blue or red, have always been controversial. For the most part, many fish cannot see red lights, so it is possible for you to leave on a red light and view your fish when they think it is completely dark.
However, since they cannot see a red light, the world appears entirely dark to them. Many of these lights are sold as being able to help your fish see the tank at night, which is not necessary. If they are able to see red and/or blue light, as bettas can, leaving this light on will only disrupt their sleep pattern.
Even if the aquarium night light is a different color and has slightly fewer LED lights than the daylight, it is still shining a bright light in your fish’s face. Unlike humans, fish do not have any eyelids to cover their eyes, and their irises respond incredibly slowly to changes in light. It would take nearly an hour for their irises to expand to take in light and adjust to a night setting. Leaving the light on would prevent them from properly using their eyes.
In addition, with the light still on, your fish will rely on their eyes instead of their sixth sense. Their sixth sense is more effective than their eyes and allows them to sleep, so leaving the light on makes it more likely for your fish to run into something and injure themselves than if you left the light off.
What Happens if Your Fish Can’t Sleep?
So, if your fish can’t sleep at night for some reason, why can’t they sleep during the day? Given their abnormal method of sleeping by resting only half of the brain at one time, this is very difficult for them to accomplish with lights on, particularly because both eyes will constantly be receiving light and signals.
They do not have a way to close their eyes, and most fish tanks do not have cave decorations large enough to create an extremely dark environment on the interior. Even if they were able to find an area dark enough for them to sleep, sleeping during the day at inconsistent times would run their sleep cycle.
Fish need to sleep in order to replenish their minds and stay healthy, and without proper sleep, their immune system is the first thing to go. The water of any aquarium constantly has pathogens in it, but they normally are unable to infect your fish due to their immune systems.
However, once the immune system is weakened, your fish is open to all sorts of infections. They can suddenly develop anything from fin rot to kidney failure to blood poisoning, some of which will kill your fish in just a matter of days. Luckily, these infections are quite rare, and your fish is just likely to get bad fin rot.
Betta fish do sleep in their own unique way. While they do not do so in a manner that we would be able to replicate, they sleep during the dark parts of the day just like we do. Without the dark parts of the day, they are unable to use their sixth sense effectively and will be unable to sleep, which can disrupt the functioning of their whole bodies. Therefore, it is important to be familiar with how your little friend sleeps, in order to keep them happy.