Emperor Tetra: Species Profile

Category: Tetra

Common Names: Emperor Tetra, Rainbow Tetra

Scientific Name: Nematobrycon palmeri

Family: Characidae

Minimum Tank Size: 10 Gallons

Care Level: Easy

Temperament: Peaceful

Max Size: 1 ½ Inches

Temperature: 72-80 F

pH: 6.0-8.0

Tank Level: Bottom to Middle

Colors: Silver, Black, Pink

Diet: Omnivore

Breeding: Moderate

Emperor Tetra Close up with Plants

Emperor Tetra Species Overview

Emperor Tetras aren’t the most popular variety of tetras. The emperor tetra is a little less flashy than other tetra species. However, this fish is a freshwater aquarium mainstay, easily found in your local store. It’s also straightforward to care for.

Whether a beginner or a seasoned pro, the emperor tetra offers an opportunity to add an intriguing and easy-to-keep fish to your tank.

Distinguishing Features

The emperor tetra is relatively long, and its body resembles a sideways teardrop, tapering to a slender tail.

Emperor tetras typically have a base color that is a neutral gray, often with a bluish tint. The scales of an emperor tetra have an iridescent quality that makes them shimmer, particularly in low-light conditions. Sometimes, their bluish tint will verge on purple as they swim in the shadows of your tank.

They have a dark black stripe running just below the midline of their body, starting at the tip of the tail and typically fading out to a smudge under the eye and through the mouth. Their fins have a swept-back appearance, and the tail, in particular, looks like a spade or a trident, with a distinct top, bottom, and middle section.

Depending on the specimen, you might see a blue line along the black stripe. Some fins, particularly the anal fin, may have a yellow edge. There may even be a faint redness where the fins meet the body. These subtle variations can combine for unique patterns among your emperor tetras.

Emperor Tetra with Plants in Background


Emperor tetras (Nematobrycon Palmeri) is native to Colombia and is found throughout the San Juan and Atrato river basins. These waters tend to have rich, heavy vegetation and mild currents. The slow flow of the water makes for easy swimming, and the rich vegetation creates a relatively dark environment.

There is typically a sandy substrate that is easy to disturb but also quick to settle. Accordingly, the water is fairly clean and clear.

The emperor tetra’s native waters are fresh and usually between 72 and 81 degrees Fahrenheit. A touch of brackishness won’t hurt a tetra, but saltwater isn’t conducive to tetra survival.


The average emperor tetra is about two inches long when fully grown. Some individuals can get a little bigger, but anything over 2.5 inches is very rare.

The male emperor tetra tends toward a longer, heavier, and pointier body. Their dorsal and caudal fins are lengthier, and their tail fin’s center spire is longer than the female’s.


A well-cared-for emperor tetra can live longer than six years. The typical lifespan is about five years in a clean and healthy environment. These fish enjoy swimming in groups, so if you have only one or two emperor tetras in your tank, they may not survive or thrive as long as those who live in a larger school.

Emperor Tetra with Blue Background and Plants


Emperor tetras are sexually dimorphic, meaning they are distinguishable by gender. The male emperor tetra is leaner and longer than the female. The female tends to be plumper, rounder, and sometimes less colorful.

In addition to their size differences and some subtly longer fins on the male, male and female emperor tetras also have different color eyes. Females have green, shimmery eyes with a metallic hue. Male eyes are similarly metallic but blue.

If you put a male and female emperor tetra side by side, you’ll also see that the center spire of the male’s tail extends past the top and bottom portion. This extension gives the tail a trident-like appearance.

As a species, emperor tetras tend to be quite docile and peaceful. But, particularly in small tanks, males can become aggressively territorial as they try to dominate their space. This aggression warrants keeping an eye on your fish and perhaps acting to remove a troublesome male from your main tank.

The good news is that a larger tank can help minimize aggression, and the attempts to dominate are rarely violent or deadly.

Tank Parameters

When setting up a tank for emperor tetras, you want to mirror their natural environment.

Minimum Tank Size

Emperor tetras like to swim in groups. They’re not true schooling fish, but they don’t like to be all alone.

If you desire a single-species tank with only emperor tetras, you should pick a tank that’s at least ten gallons. At a minimum, you should have six or eight emperor tetras. If you up the number to more than that, you should move up to a twenty-gallon tank.

When designing a multi-species community tank, it’s better to use an even larger tank of thirty gallons or more. This space allows all of the community swimmers to establish territories without aggression.

Emperor Tetra near Dark Gravel

Water Parameters

The water in your emperor tetra tank needs to match their native habitat.


The ideal temperature for emperor tetras is between 73 and 81 degrees Fahrenheit. You should aim for a consistent temperature near the middle of that range.


Emperor tetras can tolerate and adapt to water with varying pH. An acidic pH of 5 up to a slightly base pH of 7.8 is acceptable. However, these are extremes.

For the best results, you should aim for a consistent and mildly acidic pH.


There shouldn’t be any sodium in your emperor tetra tank. They can tolerate very slightly brackish water, but it’s not healthy for them.

Additionally, you should try to keep your water soft. While emperor tetras can adapt to hard water conditions, they will require more frequent water changes. You can reduce the hardness of your water by using a filter to remove minerals from your tap water, or you can buy distilled water.

Close up of Emperor Tetra

Tank Setup

An emperor tetra tank’s environment should match that of the South American rivers that are native to this fish.


Ideally, your emperor tetra’s tank will have a fairly dark substrate. This dark substrate helps create a calmer, more subdued environment that mirrors their native waters. In general, sandy substrates are better than gravel, but a mix of the two will work.

Avoid any substrate that is sharp.

Another advantage of a darker substrate is that it will help show off the natural iridescence of your emperor tetras.


Decorations aren’t strictly necessary for an emperor tetra tank. If you want to add some, driftwood, rocks, and small caves are ideal. Some large castles, like those with hiding places inside, will also work well.


Plants should make up a significant portion of your emperor tetra’s tank environment. Floating plants provide shade from the sun in their natural environment. Similarly, grasses and other bottom-growing plants provide hiding places throughout the tank, just like in the river.

You should incorporate a fairly large amount of vegetation in your emperor tetra tank. This vegetation gives your fish lots of nooks and crannies to explore and reduces the chances of aggressive behavior.

Some of the best plants to use include

While shade and hiding places are essential, balance them with ample free water for swimming.

Two Emperor Tetras Swimming in Front of Plants


Subdued lighting is best for a tank with emperor tetras. Their natural environment offers plenty of shade from the sun and ample places to hide from aggressors or territorial fish nearby.

You may need to buy a low-powered light or use a filter to attenuate its brightness. Consider all the light sources around your tank. If there is a lot of sunlight, you may need to put the tank in a shadier part of the room or use a curtain to help keep things relatively dim around it.


Adequate filtration is crucial for any freshwater fish tank. Since emperor tetras don’t enjoy strong currents, your filter should only create a mild current. Don’t choose an oversized filter that makes it hard for your fish to swim.

You may also want to consider using a peat element in your filter. Doing so can help reduce water hardness and may also help get rid of ammonia in the water.


A quality heater with a thermostat should be able to maintain a temperature of about 76 degrees for your emperor tetras. They can tolerate a wider range, but that’s just about the middle of it.

You should aim for consistency.

Emperor Tetra over Sand and Driftwood


Emperor tetras aren’t picky eaters. In nature, they eat crustaceans, insects, larvae, algae, worms, and more.

Their diet in your tank should offer some variety, but the emperor tetra remains pretty happy with a diet of dried fish flakes or pellets. However, you can promote the visibility of their colors by feeding them some live or frozen foods, like brine shrimp or mosquito larvae.

Whatever foods you use, consider how small these fish are and refrain from adding big chunks that might lead to choking or difficulties with digestion. Emperor tetras won’t eat food that sinks to the bottom of the tank.

Since these fish feed opportunistically in the wild, you want to offer two or three feedings spaced throughout each day. Any food that’s not eaten within two minutes needs prompt removal.


Breeding emperor tetras is pretty easy. It may even occur naturally, especially if you are keeping a large school in your tank.

To encourage breeding behavior, you can use live and frozen foods rich in protein as a more significant part of their diet. When a female is getting ready to breed, she will become noticeably plumper as she carries eggs.

Set up a separate breeding tank for your male and female pair. Match its conditions to the main tank, including ample vegetation. Don’t put more than one pair in a tank, or they may start to become aggressive.

Bump the temperature up to about 82 degrees, and keep the water soft, with a neutral pH. The breeding tank should have a very gentle filter, as the fish fry can be sucked into strong filters.

When the female is ready, she will spread her eggs around the tank, as the emperor tetra is a scatter-breeder. You should expect to see between fifty and 150 eggs, and the male will swim around fertilizing them.

As soon as breeding is complete, remove the breeding pair. Otherwise, they may begin to eat their own eggs. Then, keep a sharp eye out during the next two days. Within that time frame, you’ll see the tiny fry start to swim. Feed them a diet of infusoria, transitioning to brine shrimp as they grow.

Keep the fry tank’s pH consistent and dark, as they won’t tolerate light or pH changes very well.

Black Emperor Tetra with Leafy Plants

Common Diseases

To avoid the most common freshwater diseases, keep your emperor tetra tank in good condition. Perform partial water changes, and maintain your tank’s filter properly.

The three biggest issues to watch out for are Ich, gill flukes, and various infections.

Ich is a common freshwater parasite that attaches itself to your fish, resulting in lethargy and scratching behavior. You may even be able to see small white spots or tendrils on your fish’s body.

You can treat Ich with over-the-counter medications, and you may have to raise the tank’s temperature. It’s a good idea to quarantine any fish showing signs of Ich right away, as Ich is quick to spread in a closed community like a fish tank.

Just like Ich, gill flukes are a parasite. They can latch onto the gills of an emperor tetra. You can avoid them by keeping the water clean. There are commercial remedies available, but as the saying goes, an ounce of prevention is worth twice the cure.

The same goes for any of the other bacterial or fungal infections common to freshwater fish tanks. They are 100% preventable with good maintenance.

Potential Tank Mates

In general, peaceful fish found in similar native waters are ideal tank mates for emperor tetras. They will all tend to enjoy similar tank and water parameters. The best swimmers to add to a tank with emperor tetras include:

  • Other tetra species
  • Cory catfish
  • Guppies
  • Gouramis (Dwarf, Sparkling, Honey, and Pearl especially)
  • Celestial pearl danios
  • Platies
  • Freshwater snails

Wrap Up

The emperor tetra has a regal bearing, and it holds a distinguished place among all freshwater aquarium fish. They are docile, intriguing to look at, and relatively easy to care for and breed.

With a clean tank and a bit of consistency, you can keep your emperor tetras alive for five years or more. Since they enjoy swimming in the middle of the tank, you can add top and bottom swimmers around them for an ideal habitat, just like in their native waters.

If you think an emperor tetra group is right for your tank, get some today!