Emperor Tetra (Nematobrycon palmeri): Ultimate Care Guide

Common name(s)Emperor Tetra
Scientific nameNematobrycon palmeri
OriginWestern Columbia, rivers of San Juan
Temperature23°C to 27°C
SizeBetween 4cm to 5cm
Minimum tank sizeMinimum of 10 gallons, varies through number of individual fish and potential other species
Food & DietVaried, mainly worms and crustaceans
Lifespan6 years average
Water pHBetween 5 and 7, slightly acidic
Tank matesMost other species of a similar size and temperament
BreedingHappens naturally and often, but can be influenced
Common diseaseCommon fish diseases that affect most species such as Ich and other infections

Emperor Tetras, or Nematobrycon palmeri, is a species of characid fish which can be found in Western Columbia, more specifically the rivers of San Juan. They have lean, elegant bodies with a dark blue coloured line along their side while the rest of their body is a blueish grey. Being low-maintenance and a peaceful species, they are a great choice for beginners who are just starting their aquarium journey! They can also be kept with a range of species, numbers and size making them appealing to those with many setups, whether it be a large community or just a pair.

Emperor Tetra
Emperor Tetra

Emperor Tetra Care

As mentioned previously, Emperor Tetras are an easy species to take care of, they will thrive in just simple conditions, though you should still take care to ensure that all of their requirements are met and that they stay happy and healthy. The ease of care makes them and easy species for an aquarium as there are more species that will share their range of conditions in terms of water pH, temperature and setup.


Emperor Tetras will be content in temperatures between 23°C and 27°C, though it is best to stick in the middle of this range as it will ensure their health and will help them to thrive. Water temperature can be controlled naturally by monitoring the direct light the tank is exposed to, any nearby heaters or fans, or a chiller. It is best to keep the temperature constant as the fish will adapt to this more over time and large fluctuations may cause adverse effects on their health.

Water pH

The water pH for the Emperor Tetras tanks should be between 5 and 7 which tends to be slightly acidic. This factor is important to keep stable and correct as a lack of control may lead to damaging health issues as it influences the water chemistry. It is important to test the water often and monitor the pH as it can change with the introduction or decomposition of plants in the water.

Emperor Tetra Size

Emperor Tetras are a fairly small species of fish, with males growing up to around 4.5cm while females are marginally smaller, growing up to 4cm. Their small size makes them perfect for an aquarium and although they are not a schooling species, they stick together, especially in larger groups and are known to swim in some beautiful formations. Their size also allows for a slightly smaller tank which makes them more accessible to those with a slightly smaller budget or lack of means for a large tank.

Food & Diet

Emperor Tetras diets are very varied but most usually consists of worms and crustaceans, along with a wide range of other foods such as flakes, pellets, and occasionally bloodworms, brine shrimp and mosquito larvae. They are not picky over food, but they are an omnivorous species, so both meat and vegetables should make up parts of their diet.


Emperor Tetras tend to live up to around 6 years on average, varying for each individual fish and will depend strongly on their tank conditions, diet and treatment. Exposure to contagious diseases within an aquarium will significantly reduce their lifespan, especially if not treated quickly and properly. Other factors such as how the tank is set up and their tank mates may also contribute to other issues such as stress which may shorten their lifespan.

Emperor Tetra
Emperor Tetra

Tank Size

The tank size for Emperor Tetras will strongly depend on how many are in a group or if they are being housed as part of a larger aquarium. A small group of around 5 fish would be happy in a tank of 10 gallons, but larger groups would need upwards of at least 20 gallons to thrive. If they are a small group along with other species and groups, the individual situation should be considered of the other individual fish’ requirements.

Tank Setup

Similar to their natural environment in Western Columbia, Emperor Tetras prefer dimmer lighting with a significant amount of vegetation to allow for hiding places and shelter, reflecting the conditions of the wild. Dark substrate may be used to mimic the seabed in the rivers, though any substrate would tend to work due to the lack of light. Other plants, including floating ones to give the tank depth, leaves and driftwood would add to the tank, although it is important to make sure that they still have plenty of room to swim and that they will not get caught or injured, making a larger tank more appealing for some people. A filter will also be needed to ensure the quality of water is suitable, though make sure to ensure there is no strong current as Emperor Tetras are not adapted to these conditions. If the current is too strong but no equipment can be changed, the plants can be positioned in a way to block as much of it as possible.


Telling male and female Emperor Tetras apart is very easy as they have some obvious differences. Females tend to be significantly smaller and rounder with metallic green eyes instead of blue. Males also usually have their dark stripe extend into their tail as a third, middle pike on their tail. It is important to distinguish between the genders, especially for smaller groups to prevent aggressive male behaviour as well as allowing for more successful breeding if the pair are to seperated.

Emperor Tetras are an easy species to breed, with reproduction occurring naturally without any special circumstances as long as the conditions are suitable for them. However, there are a few ways to speed up the process should this be necessary. The breeding pair should be separated from the community in a tank with a slightly higher water temperature on the warmer side of their scale, they should be fed live food and there should be plants and leaves to protect the eggs once laid as this species has been known to eat their eggs. Once the eggs have been laid, the pair can return back to their tank and the eggs should begin to hatch within a couple of days. Only introduce the new fish into the community tank once they are able to swim properly on their own, which is usually around a week. Make sure that the tank is suitable for this increase in numbers as a minimum of around 50 eggs will be laid at once.

Common Diseases

Emperor Tetras, like many other species of fish will suffer from common diseases such as Ich and a variety of other parasites and infections. Ich is a parasitic disease categorised by iconic white spots dotted across an infected individual’s body and can cause many symptoms and health concerns such as a loss of appetite and even death if not treated. It is extremely contagious, especially within a tank meaning it needs to be identified and treated quickly so as not to endanger the whole community. If one fish has Ich it is best to separate them, treat them and keep a close eye on the rest of them to minimise the risk of spreading. Other infections and parasites will affect them like other species so it is important to keep an eye on any strange behaviour such as lack of appetite, changes in fins or scales and any strange bumps or spots.


Emperor Tetras are a very peaceful species making them perfect for an aquarium as long as they are housed with suitable tank mates. However, males have a more aggressive temperament, as a way to assert their dominance, especially when there is more than one male in a group, so it is best to have one male in a group of females to prevent fighting or injury. This happens more frequently in smaller tanks do more than one male may be housed in the same aquarium if it is large enough and they do not feel threatened.

How many Emperor Tetras to a tank?

Emperor Tetras are a very flexible, adaptable species and will function and be content in a group of pretty much any size. Around 5 to 8 fish is an optimum number as they may not only be happier socially, but it will also allow for larger, more impressive displays. If they are kept in a group of this size, it is best, as mentioned before, to only have one male, the alpha male, as otherwise they will fight for dominance. Despite this, Emperor Tetras would also be happy in anything down to a pair or even in larger groups, solely depending on personal preference.

Are they fin nippers?

Some Emperor Tetras will be fin nippers, while others will never portray this behaviour, it is down mostly to the nature of the individual fish, however, some factors may see an increase in this behaviour. Keeping too many in one group may lead to fin nipping due to stress over competition of food and possibly a lack of space. It also may occur due to specific territorial disputes which may be able to be reduced by ensuring the fish have plenty of space and that there is enough food for each fish. If there is too much issue with fin nipping, although it rarely causes significant harm to a fish, they may need to be separated to prevent the behaviour from happening. Fin nipping may also occur between species which may indicate that they are not suitable tank mates for each other.

Tank mates

Emperor Tetras will fare well with most other species of a similar peaceful temperament and optimum conditions to allow the entire community to thrive. It is important not to keep them with larger species as they may mistake the Emperor Tetra of a significantly smaller size as food. Other types of Tetra may be considered such as the Serpae Tetra or potentially some types of Danios or Gouramis. Emperor Tetras may get along with Bettas, however, it depends on how large the specific species grow to and whether they may mistake them as food. As well as this, they will not get along if the Emperor Tetras begin nipping their fins.

Buying Emperor Tetras

Emperor Tetras are an extremely popular species of fish as they are suitable for those of any skill level and their stunning displays make them very rewarding. Because of this, they can be found for around $3 a fish in many physical pet stores as well as online.

Emperor Tetra Types

A Purple or Blue Emperor Tetra has a mainly cream coloured body with a dark stripe running down their body that may take on a more purple or blue colouring as they mature further and breed. They make for the most beautiful displays as they are brighter and more stunning than those with duller colours.

Rainbow Emperor Tetras are the rarest type of Emperor Tetra and can only be found in small forest pools around Rio Calima. They have similar tank requirements to other species of Emperor Tetra, though dry leaf litter may be included as it also provides a healthy food source for them as the leaves break down. In most lights, the Rainbow Emperor Tetra has a silver sheen with the iconic dark stripe, however, different lighting will reveal all of the beautiful colours spanning their bodies.

Some other species of Emperor Tetras can be distinguished by their colour such as the Black Emperor Tetra and Red Emperor Tetra, however, they all share very similar tank conditions, and the main difference is solely the aesthetics of their scales and fins.

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