Why Do Tetras Glow? (Do They Glow All The Time?)

Image of a glowing tetra

Tetras glow because of their radiant color. The radiant color of tetras is due to the physical and genetic makeup of this fish. Tetras have cells called chromatophores in them. These cells reflect and scatter particular wavelengths of light to produce the characteristic and colorful glow of tetras.

Let’s discuss this in greater detail now.

Why Are Tetras So Colorful?

Most varieties of tetras have beautiful, bright colors.

They have a glowing, iridescent effect which makes the fish unusually attractive.

Their colors almost seem to bounce off the fish, and they shine brightly.

This fluorescent color is the effect of years of evolution.

It is a natural process that enables the fish to escape predators and other forms of danger.

You may already know that tetras come from the warm river basins of South America.

These regions have thick vegetation, and the rivers flow through thick forests.

The huge trees block most of the sunlight, and these fish live in dark waters for most of the year.

So, their bright coloration and glow are a natural adaptation that helps them identify their kind in the murky waters they live in.

It could be nature’s way of protecting the small creatures and helping them find each other and stay together.

Now, an interesting theory is that most brightly colored fish are very tiny.

Such fish usually prefer to live in schools with their kind. They travel everywhere in a group.

When huge numbers of such bright fish travel together, the fast-moving light can confuse predatory animals.

It reduces their risk of being caught and eaten. So, their bright colors serve as an effective defense mechanism.

What Causes The Bright Colors And Radiant Glow Of Tetra Fish?

A closer look at the skin of tetra fish offers a clear picture of what causes their characteristic glow.

Bright colors and the characteristic glow of fish are usually caused by the presence of special cells called chromatophores.

These cells absorb light rays and reflect or scatter only certain wavelengths of light. Hence, they produce specific skin colors.

To understand how tetras get their vivid glow, we should understand the working of chromatophores in closer detail.

How Do Chromatophores Produce The Characteristic Glow Of Tetra Fish?

Chromatophores are of different types. We can broadly classify them into two main types: structural and pigmentary.

Pigmentary chromatophores are concerned with specific colors only.

For instance, erythrophores are pigmentary chromatophores that are orange or red.

Meanwhile, cynaphores are blue pigmentary chromatophores.

Now, structural chromatophores do not have pigmented colors. Instead, they possess silvery hues.

These structural chromatophores are responsible for effects like fluorescence, iridescence, and reflection of light.

Tetras have both structural and pigmented chromatophores.

The color of a tetra fish depends on how these chromatophores react to different light.

Depending on the light falling on the fish, the spacing of the reflecting plates will change.

Accordingly, the fish will either glow brightly or lose its brightness.

When light falls on the skin of the tetra fish, the chromatophore layers contract.

In the presence of strong light, the layers will come close together.

When they contract, the skin absorbs light and reflects a brilliant blue-green color.

Meanwhile, if there is less or no light, the chromatophores relax and move apart. Consequently, the color of the fish becomes dull.

Tetras will also lose their colors when they sleep or are sick.

In such situations, the fish will have low energy, and hence the layers will relax and expand.

So, when the angle and position of the chromatophores change, the fish can appear bright or dull.

Do Tetras Glow All The Time?

We already saw that the glow of tetra fish is affected by the light falling on it.

Apart from exposure to light, tetras also glow when they are excited or aroused.

When the fish are very bright, they look more attractive and appeal to mates.

So, the brighter it glows, the more likely it is to find a partner.

The quality of nutrition also plays a role in how bright and colorful a tetra fish is.

When you feed tetras with the right nutrients, they appear brighter and stronger.

Their colors are also affected by the quality of water and the stress they are subjected to.

Nonetheless, for tetras to glow and display their beautiful colors, they should have the right set of genes and DNA for the purpose.

When Do Tetras Lose Their Glow And Bright Colors?

Tetras look bright and radiant when their energy levels are high.

When they are active, the light-reflecting cells in the skin contract to produce bright colors.

Tetras temporarily lose their bright glow when they rest or sleep. Lack of proper lighting will also affect their colors.

The activity of the chromatophores depends on how much light is present.

So, their colors may pale or fade in the absence of light.

Tetras will also look dull when they are ill or stressed. This fish is highly sensitive to water quality.

If you place them in unhygienic tanks and the water quality deteriorates, the fish will lose its beautiful coloring.

Tetras also tend to feel stressed when the water parameters change. As a result, the fish will lose its bright colors.

Hence, it is not unusual for tetras to look dull after a water change.

However, this fading should be temporary. The fish will bounce back and regain its bright glow once it adjusts to the water.

Parasitic infections and other diseases can also affect the color and glow of tetra fish.

To ascertain the cause of any dullness, observe your fish continuously.

If its original color is not restored in a day or two, you can suspect the fish to be sick.

In this case, investigate the cause and treat it promptly to help the fish recover quickly.

Why Do Neon Tetras Glow?

Neon tetras are one of the most identifiable aquarium fish due to their bright and lively colors.

The fish has a sensational turquoise blue color along the length of the body.

It also has a red stripe running from the middle of the body to the tail fin. The red and blue coloring creates a spectacular effect.

The iridescent color of the neon tetra is due to how its skin cells react to light.

The fish has microscopic structures on the skin surface that reflect light and produce a distinct glow.

By changing the angles of these microscopic structures, neon tetras can change the color of their bodies.

It helps them appear bright blue for a moment and a dull violet or indigo the next.

Interestingly, neon tetras can turn off their bright colors when they desire. They will usually do this when they feel threatened.

The bright neon colors of the neon tetra also fade when they are asleep.

This fish stays awake for twelve to fourteen hours a day and sleeps for the rest.

While it sleeps, the skin cells relax and move further away.

Hence, the color fades, and the fish takes on a pale appearance. It makes it less conspicuous and helps it to escape enemies.

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