Do Neon Tetras Sleep?

Do neon tetras sleep? Believe it or not, Neon Tetras do sleep. The small, silvery fish – with their characteristic red tails and blue stripes – are known to change their behavior in the nighttime hours, greatly reducing their movement, swimming only in certain areas, and even changing colors. This is believed to be an indication of the species sleeping at night, or at the very least a means of reducing their metabolism and conserving energy.

Neon Tetras (Paracheirodon innesi) are a small schooling fish that are native to warm (68 to 77 degrees Fahrenheit) freshwater, usually the slow-moving black waters of tropical river basins. As such, their swimming behavior is limited in nature, and even more so in aquarium settings. Neon Tetras are a fairly active species in captivity, especially during the day, swimming in schools of at least six or more. In aquariums, the schools are also known to favor some plant cover.

Like all fish (except sharks), Neon Tetras do not have eyelids — and like all fish, they do not have a neocortex. The neocortex is the part of the brain that in mammals, provides motor skills, spatial awareness, consciousness, and sensory perception (and in humans, the ability to use language). At any rate, activity levels in the neocortex will change greatly during sleep in humans and mammals — none of which is present in fish, including the Neon Tetra.

So with these things being the case, it may be difficult to tell if or when the Neon Tetra is asleep (or not). Other animals have specifically measurable brain activity when they sleep — and besides that, they usually sleep with their eyes closed. But there are other ways to tell when fish (including the Neon Tetra) are sleeping, or at the very least, putting themselves in a less active state.

Signs of Neon Tetra Sleep

If you are an aquarium owner with a school of Neon Tetras in your tank, there are visible ways to tell when the school (or an individual fish) is at rest, or asleep. These can include changes in appearance, movement, and location in the tank. As the fish is normally active during the day, these changes are more likely to happen during the night. The following sections will attempt to illustrate the visible changes in the Neon Tetra during sleep periods.

Do neon tetras sleep
Believe it or not - Neon Tetras do sleep!

Changes in Appearance

A Neon Tetra is normally a brightly colored fish. It has a short, silvery body with somewhat stunning light blue streak that runs along its back, from its eye to roughly the first quarter of its tail (it has also been described as an iridescent blue-green). In addition to this, the Neon Tetra also has a vivid red tail stripe that goes halfway up its body, just below the blue stripe.

During the night hours, these colors change. The blue-green area becomes a deep violet and the red tail fades in color. When light changes in the Neon Tetra’s environment, or when the species goes through different emotional states, the spacing of its blue plates change. This causes the top stripe to darken. Movement of cell pigments causes the red tail section to lose color — and both of these changes are believed to function as camouflage during nocturnal hours, at least in the wild.

If you’re an aquarium owner with a school of Neon Tetras, chances are you may have seen the fish change color in this way at night. Then, as daylight arrives (or, if you make adjustments to the aquarium’s lighting) the Neon Tetras turn back to their original colors. This is a sign of the fish sleeping, or otherwise recovering energy.

However, you should try not to associate all color changes to Neon Tetra sleep patterns. When a member or members of the school turn white or fade in color, it could also be a sign of disease. The most common of these diseases is Neon Tetra Disease (NTD), an ailment caused by an ingested fungal parasite. When a Neon Tetra consumes a dead fish or food contaminated with NTD, it can become infected. If it remains among the school, it has the potential to infect others.

This disease also causes the fish to lose their color, and fade to whitish hues. The difference here though, is that the infected fish will also puff up in appearance, swim slower (and more irregularly) and show a curvature in their spines. These are a signs of an infected fish. If the infected fish dies, other Neon Tetras may eat it. For these reasons the fish suffering from NTD must be separated from the school immediately.

Changes in Movement

During the daylight hours, a school of Neon Tetras is fairly active. It will swim in all areas of the tank (if in an aquarium) and will prefer some form of plant cover if available. Neon Tetras are of a peaceful nature, and will get along with other fish species (pencil fish, hatchet fish, and small rasboras) of a similar temperament.

At night, Neon Tetras become mostly static. They float in a horizontal position, swimming minimally, only moving their mouths, gills, and perhaps their pectoral fins. This is an adjustment that fish make to have a continuous water flow through their gills while they sleep. If the fish do not stay at least partially active, they will lose their source of oxygen.

As with color changes, fish whose movements change may not always indicate that the fish is sleeping. They could be diseased or deceased. This is especially the case if the Neon Tetras are in a vertical position, upside down, or otherwise not moving at all. Rarely (but it still does occur), Neon Tetras will also “play dead” if they feel threatened or want attention. It is therefore important to observe Neon Tetras casually to see if such things do occur.

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Changes in Location

Neon Tetras will swim in several areas of an aquarium tank during the day. As stated before, they are an active species that prefer to swim in schools and will find shelter among plants (or rocks) if necessary. In the wild, predators will pursue them — and as a result, the Neon Tetra must remain fairly active.

Fish do not lose this instinct when they choose areas in which to sleep. Many fish species will choose low or remote areas to rest. These can include hiding places near plants, rocks, crevices, coral, and driftwood. Some species will completely bury themselves under sand or mud. These areas are all intended to serve as a safe hiding places from other fish and larger animals.

Neon Tetras are no exception. At night, sleeping Neon Tetras tend to gather in the low areas of an aquarium tank. You may likely find a school of the fish sleeping towards the middle area of the tank, or in a place among plants. But in any case, expect the Neon Tetras to remain low in the tank, and not the places in which they usually swim during the day.

Conclusion - Do neon tetras sleep?

Like other fish, Neon Tetras show visible indications that they sleep or rest in some way.  They will change their color as night comes in a way to camouflage themselves from other animals. They will remain in a roughly horizontal position, stationary except for small movements in their lips, gills, and fins. (Do all fish sleep? – Check out this article).

Also, they will take an opportunity to change their location, with tanked aquarium Neon Tetras settling at low locations near the center of the tank, or near some form of cover. All of these things are done with the purpose of self-preservation. The less the Neon Tetra is active at night — and the more it is disguised — the greater chance it has of surviving attacks from other animals, and getting the rest it needs for the day ahead.

That said, owners of the Neon Tetra should not confuse this behavior with that of death or disease. A single dull-colored Neon Tetra with an irregular swimming pattern is a sure sign of Neon Tetra Disease (NTD) — and must be separated from the rest of the school as soon as possible. Neon Tetras that are floating vertically, belly up, or at other angles could be diseased or dead. Finally, a Neon Tetra may pretend to be “dead” if it is scared or threatened. In this case, the cautious owner will pay close attention to their school’s behavior.