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Congo Tetra – Phenacogrammus interruptus


Congo Tetra

Tetras are amongst the most popular aquarium fishes. There are probably more than 150 distinct species of tetra from which the aquarist may choose and this includes a large number of visually stunning fishes that are bound to enhance any home aquarium.

Is the Congo Tetra a good community fish? The Congo Tetra is an excellent community fish and gets on with most species. It is an ideal species for relatively inexperienced aquarists and is readily available.  The Congo Tetra is a “rhomboid” Tetra in shape. The Congo Tetra is quite easy to sex because the male tends to be larger, more colourful and have longer, more ornate finnage.

Key Facts

CategoryKey Facts
Common name(s)Congo Tetra
Scientific namePhenacogrammus interruptus
FamilyCharacidae
Originate fromCentral Congo River Basin in Africa
Care requiredEasy to care for and hugely popular
TemperamentPlacid, shoaling fish
Colour & FormBlue over dorsal area then red, then orange returning to blue/black around abdomen. Male is larger with fabulous finnage.
LifespanUp to 5 years
Adult size3.5 inches (female around 2.75 inches)
DietOmnivorous – eat aquatic insect larvae in nature
Aquarium size48 inches in length or greater
Compatible withMost other Tetras, Barbs, Danios, Guppies and other livebearers, dwarf cichlids, smaller Gouramis, catfish and loaches
Avoid keeping withLarge and/or aggressive species and fin-nippers
BreedingEasy if you put the fish in the right environment.
Water temp73 – 79 Fahrenheit
Water pH6.0 to 8.0
Water hardness (dGH or dH)1 to 20 dGH

Origins of the Congo Tetra

Tetras, as a “family” of fishes belonging to the biological family Characidae are found in nature in Africa, Central America and South America.

The Congo Tetra originates from the central Congo River Basin in Africa. The vast majority of Congo Tetras available to aquarists are captive-bred and the species is hugely popular.

Characteristics of the Congo Tetra

As you can see, the Congo Tetra is characterized by its beautifully coloured body. The Congo Tetra will grow to up to 3.5 inches (males) or 2.75 inches (females) in the aquarium and live for around five years. 

Congo Tetras prefer fairly neutral water with a pH of 6.0 to 8.0 with a temperature range between 73 and 79 degrees Fahrenheit and up to 20 dGH.

It is generally recommended that Congo Tetras are kept in peat-filtered aquariums.

The Congo Tetra is a shoaling fish and should be kept as a group of at least six fish, though a shoal of, say, ten or more fish is highly recommended. Having plenty of vegetation to break up lines of sight will also help to protect your Congo Tetras from predation but it is obviously advised that Congo Tetras are not kept with predatory species.

The adult male Congo Tetra shows, a blue stripe, front to back over the dorsal ares, changing to red, then to orange before returning to blue/black at the abdomen.

The fins of the male Congo Tetra are really rather ornate and is a hallmark of this species. It is easy to distinguish between the sexes of the adult Congo Tetras, as the male is bigger, has longer, more flowing dorsal, caudal and anal fins and its colouring is rather more striking that the female. When the female is carrying eggs (gravid), as her lower abdomen will become more distended than the male. 

The Congo Tetra has a much deeper body than, for example, a Neon Tetra, being much more rhomboid in shape. 

The Congo Tetra tends to inhabit the middle and upper areas of the aquarium (top to bottom). That said, it is a vigorous fish when breeding and will readily traverse the entire aquarium.

The Congo Tetra is, by nature, a shoaling fish and it is generally recommended to purchase six or more fish, as their nature is to swim together as a shoal and they will tend to thrive much better as a shoal. Congo Tetras are excellent community fish and are ideal for aquarists with moderate experience, as they don’t tend to have aggressive tendencies towards other species. It is advised not to include Congo Tetras in an aquarium containing predatory species, as their wellbeing may rapidly deteriorate. Similarly, avoid fin-nipping species. It is often the case that mature males will show some damage to their otherwise fabulous finnage.

Congo Tetras, like most rainforest species, prefer a shaded and well-planted tank, as they can hide from predation, so consider including floating leaves and/or allowing vegetation to grow so that it floats on the surface of the water to provide shade.

It is generally advised that the minimum tank size for Congo Tetras should be one of 48 inches in length or more due to the size, levels of activity and shoaling nature of the species, which will enable a small shoal to move around freely. The tank should be well-planted but with clear areas where the fish can swim freely. The water should only have gentle movement.

The general rule for Tetras is that by keeping six or more of the same species in an aquarium they will be fully aware of which is male and which is female and they will act accordingly.

Most (but not all) Tetras have an additional fin which identifies them as being Tetras and the Congo Tetra is no exception. If you look between the dorsal fin and the caudal (tail) fin of the Congo Tetra you will observe a tiny, additional fin, known as the adipose fin. The purpose of this fin is not fully understood but, if it is present on a freshwater tropical fish then you can be pretty certain that the fish is a Tetra.

Tetra comes from the Greek word “Tetragonopterus” which means square-finned and appears to relate to the four fins on vertical plane of the fish (dorsal, adipose, caudal and anal fins) which span the central line of the fish (when viewed from above or below, front or rear) and are not present as a pair (e.g. the pectoral or pelvic fins).

Congo Tetra – Video

How do Congo Tetras breed?

Tetras, in general, will scatter eggs by laying them over fine plants such as Cabomba, Fontanalis or Java Moss.

Congo Tetras, like most species, are noted to leap above the water surface during breeding and in general, so it is advised that the tank should be covered to mitigate the risk of losing fish.

As the female Congo Tetra becomes ripe with eggs, the difference between the sexes becomes even more evident. If you plan to attempt to breed Congo Tetras then it is recommended that you have a breeding tank prepared. Such a tank can be empty but you may wish to include a mesh or grid under which the fertilized eggs will fall and/or a sterilized breeding mop.

That said, Congo Tetras will breed in a community tank and, if the tank is well planted, it is likely that at least a few fry may survive to reach adulthood.

Some say that a novice may find it difficult to breed Congo Tetras but, in my experience, by understanding the conditions that are ideal for breeding, most species will breed quite readily, as it is natural for them so to do and, in general, nature finds a way.

I have observed Congo Tetras breeding readily and vigorously in quite soft, acidic water (pH 5.5 to 6.0) and less than 12 dGH.

The female will swim vigorously around the tank and, if you include two males then they will encourage her to lay her eggs by bumping into her. She will lay her non-adhesive eggs which will immediately be fertilized by the male(s) and will fall to the bottom of the tank (preferably through the mesh or trap). Once spawning is complete, remove the adults, as they are likely to consume the eggs, given the chance, and take no further parental responsibility. A mature female may lay in the order of 300 eggs.

Spawning usually takes place in the early morning.

Breeding tank for Congo Tetras

You should prepare a tank of around 20 gallons in size with mature water. The water should be at a pH of around 5.5 to 6.0, maintained using an aquatic peat filter and with a low level of light.

You may wish to introduce mosquito larvae or bloodworm as an inducement to reproduction.

The female will swim amongst the plants, laying her eggs whilst the male will swim alongside or behind her and fertilize the eggs as they are laid. Typically, the female can lay around about 300 eggs during a spawning, which may adhere to plants or will sink to the bottom of the tank.

Once the female has scattered her eggs and the male has fertilized at least some of them then the adults should be removed carefully from the breeding tank because they will have nothing more to do with the eggs but they may simply eat them.

Keep the lights off and the tank dark because Tetra eggs and fry are particularly sensitive to the light.

The eggs will hatch typically in around six days or so depending on tank temperature and conditions and the fry will become free-swimming after around five to seven days after hatching. Keep the tank unlit for the first couple of weeks or so then gradually increase the lighting.

The newly hatched fry will firstly feed on their yolk sac but, once free-swimming, can be fed infusoria (particularly rotifers) and will also thrive on egg yolk during the first two to four weeks. It is worth mentioning that immediately after hatching, fry seem quite vigorous but will soon go into a resting state before they become free-swimming so please don’t mistake this initial stage as being free-swimming.

After around four days or so add baby brine shrimp. Once the fry are sufficient in size not to be treated as a snack then they can be introduced into the community tank where they will join the existing shoal. Before moving the adolescent fish into the community tank ensure that you have balanced the water temperatures to mitigate the risk of White Spot or other diseases being triggered.

Should your Congo Tetras have a special diet for breeding?

Adult Congo Tetras don’t need any particular inducement to breed. That said, it has been suggested that adding mosquito larva may encourage them, presumably because the addition of a new food may “fool” the fish into thinking that it is breeding time. From my own experience, I would always recommend keeping all of your fish in the best possible condition at all times, as this is good for the wellbeing of your fish.

Mike Wheeler

I started keeping freshwater tropical fish in 1972 and it has been something of a passion ever since. In this website, my aim is to build up an everyman's guide to help the everyday aquarist get the best from this inspiring and entertaining hobby.

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