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Redeye Tetra – Moenkhausia sanctaefilomenae


Red Eye 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 Redeye Tetra a good community fish? The Redeye Tetra should be considered to be an excellent community fish and gets on with most species if kept as a small shoal. It prefers soft, slightly acidic water chemistry. The female is distinguishable by being slightly fuller in the body than the male. Redeye Tetras can be fin-nippers so be aware of this.

Key Facts

CategoryKey Facts
Common name(s)Redeye Tetra – also known as:
Lampeye Tetra
Yellowhead Tetra
Yellow-banded Moenkhausia
Yellowback Moenkhausia
Scientific nameMoenkhausia sanctaefilomenae
FamilyCharacidae
Originate fromThe São Francisco, upper Paraná, Paraguay and Uruguay river basins in eastern and central South America
Care requiredEasy to care for and hugely popular
TemperamentPlacid, shoaling fish but some can be fin-nippers
Colour & FormBright, silver body with white stripes on leading edges of fins, white scales ahead of caudal fin and black caudal fin
LifespanUp to 5 years
Adult sizeUp to 2.75 inches
DietOmnivorous – eat aquatic insect larvae in nature
Aquarium size36 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 species with elaborate finnage
BreedingEasy if you put the fish in the right environment.
Water temp73 – 82 Fahrenheit
Water pH5.5 to 8.5
Water hardness (dGH or dH)Up to 25 dGH

Origins of the Redeye 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 Redeye Tetra native to the São Francisco, upper Paraná, Paraguay and Uruguay river basins in eastern and central South America. The vast majority of Redeye Tetras available to aquarists are captive-bred.

Characteristics of the Redeye Tetra

As you can see, the Redeye Tetra is characterized by its high body, its silver body and red colour over the top of its eye. The fins of the Redeye Tetra are largely clear (hyaline) but with a white leading edge.

Just ahead of the caudal fin, the scales are coloured white and the caudal fin itself tends to be largely black, fading as it becomes closer to the trailing edge.

The Redeye Tetra will grow to up to 2.75 inches and will live for up to 5 years of age.

The Redeye Tetra is also known as:

  • Lampeye Tetra
  • Yellowhead Tetra
  • Yellow-banded Moenkhausia
  • Yellowback Moenkhausia

The Redeye Tetra is a very adaptable little fish because it can tolerate both clear, almost neutral water and “blackwater” which is quite acidic.

The Redeye 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, as it is known to be a fin-nipper on occasions even if it is part of a larger shoal.

Having plenty of vegetation to break up lines of sight will also help to protect your Redeye Tetras from predation but it is obviously advised that Redeye Tetras are not kept with predatory species.

The Redeye Tetra has a deeper body than, for example, a Neon Tetra and the female has a more rounded body than the male, especially when gravid (carrying eggs). The colouring of the male tends to be fuller and richer than that of the female, especially as spawning approaches.

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

The Redeye 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. Redeye Tetras are excellent community fish and are ideal for novice aquarists, as they don’t tend to have aggressive tendencies towards other species unless they are not kept as a shoal (ten or more fish are recommended). It is advised not to include Redeye Tetras in an aquarium containing predatory species, as their wellbeing may rapidly deteriorate.

Redeye Tetras, unlike most rainforest species, enjoy clear water but seem happy in a shaded 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. They are used to habitats that include decomposing wood and vegetation, which tends to make the water brown (the effects of tannins) and acidic but seem equally happy in clear water.

It is generally advised that the minimum tank size for Redeye Tetras should be one of 36 inches in length or more due to the 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 have gentle movement.

Redeye Tetras are able to thrive in water with a pH of 5.5 to 8.5 with a temperature range between 73 and 82 degrees Fahrenheit and up to 25 dGH.

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 Redeye Tetra is no exception. If you look between the dorsal fin and the caudal (tail) fin of the Redeye 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).

Redeye Tetra – Video

How do Redeye Tetras breed?

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

Redeye 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 Redeye Tetra becomes ripe with eggs, the difference between the sexes becomes even more evident. If you plan to attempt to breed Redeye 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, Redeye 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. Having a good covering of Willow Moss on the floor of the aquarium seems to provide a safe haven for fry, which can help them to survive predation in a community or single-species tank.

Some say that a novice may find it difficult to breed Redeye 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 Redeye Tetras breeding readily and vigorously in quite neutral water but soft, slightly acidic water is the general recommendation. Bearing in mind that you are likely only to purchase captive-bred specimens then it may well be that the commercial breeder has, over numerous generations, acclimatized the stock to thrive in a wider range of water conditions.

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 slightly adhesive eggs which will immediately be fertilized by the male(s) and will either stick to plants or spawning mop or 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.

Spawning usually takes place in the early morning. In nature, Redeye Tetras spawn at the start of the rainy season.

Breeding tank for Redeye 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 6.5, a dGH of around 4 or 5 (very soft) and, ideally around 80 to 83 degrees Fahrenheit 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, when the female lays her eggs during a spawning, they 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 a day or so depending on tank temperature and conditions and the fry will become free-swimming after around three to four days after hatching. Keep the tank unlit for the first week or so then gradually increase the lighting.

The newly hatched fry will firstly feed from 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 Redeye Tetras have a special diet for breeding?

Adult Redeye 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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