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Sailfin Tetra – Crenuchus spilurus

Sailfin 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 Sailfin Tetra a good community fish? The Sailfin Tetra is not really a good community fish. The male is territorial and will even spa with its own reflection so you may be better advised keeping this species in a single-species aquarium. The Sailfin Tetra is a rhomboid Tetra in shape. The Sailfin Tetra is quite easy to sex because the adult male as an elongated dorsal fin and fin marking akin to the Pearl Gourami whereas that of the female’s fine tend to be clear (hyaline).

Key Facts

CategoryKey Facts
Common name(s)Sailfin Tetra
Scientific nameCrenuchus spilurus
Originate fromAmazon and Orinoco Basins, as well as various river Basins in the Guianas in South America
Care requiredSomewhat of a specialist fish
TemperamentCan be aggressive
Colour & FormRhomboid shape, male has elongated dorsal fin and “lacy” markings on the fins
LifespanUp to 5 years
Adult sizeUp to 3 inches
DietOmnivorous – eat aquatic insect larvae in nature
Aquarium size24 inches in length or greater and dark
Compatible withRather a solitary fish and prefers low to no light
Avoid keeping withMost other species
BreedingNot generally captive-bred in the commercial sense.
Water temp68 – 80 Fahrenheit
Water pH5.5 to 6.5
Water hardness (dGH or dH)1 to 5 dGH

Origins of the Sailfin 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 Sailfin Tetra is found in the Amazon and Orinoco Basins, as well as various river Basins in the Guianas in South America. The vast majority of Sailfin Tetras available to aquarists are imported rather than captive-bred.

Characteristics of the Sailfin Tetra

As you can see, the Sailfin Tetra is characterized by its silver body which has a black patch at the caudal peduncle. The dorsal, and anal fins have orange-red tips whilst, in the female, fins are all more-or-less clear (hyaline). A male in good condition will have fin markings which I would describe as being similar to those of the Pearl Gourami.

The Sailfin Tetra will grow to up to 3 inches in the aquarium and live for around five years.

The Sailfin Tetra will avoid the light and you will see an example of this in the second video below.

Sailfin Tetras prefer fairly neutral or acidic water with a pH of 5.5 to 6.5 with a temperature range between 68 and 80 degrees Fahrenheit and up to 5 dGH.

It is generally recommended that Sailfin Tetras are kept in a peat-filtered aquarium and either as a single species or with peaceful companions of a similar size.

The Sailfin Tetra in nature is more often found in fairly “blackwater” conditions. Indeed, it is generally recognised to be, in part, at least, a cave-dwelling species so should certainly have plenty of cover and limited light.

In order to maintain the softness and acidity of the water to simulate a “blackwater” environment, it is recommended that the aquarium is filtered using aquatic peat. In addition, floating and naturally decomposing Indian Almond leaves are highly recommended. 

The floating leaves provide the shaded area that the Sailfin Tetra will dwell beneath and the decomposing vegetation provides the tannins that will effectively synthesize the “blackwater” conditions found in the natural habitat of the Sailfin Tetra.

The Sailfin 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. The ratio of males to females is recommended as being 1:2. Having plenty of vegetation to break up lines of sight will also help to protect your Sailfin Tetras from predation but it is obviously advised that Sailfin Tetras are not kept with predatory species as they are very timid.

It is fairly easy to distinguish between the sexes of the adult Sailfin Tetras, as the male has an extended dorsal fin and its finnage, in general, is quite “fancy) whilst the female is rounder (when viewed against a strong light) and, when ready to breed, the colouring of the male becomes much more intense. When the female is carrying eggs (gravid), as her lower abdomen will become more distended than the male. The male is also somewhat territorial and will even attack his own reflection, at least until he realizes that it is a reflection.

The Sailfin Tetra has a deeper body than many Tetras being much more rhomboid in shape. 

The Sailfin Tetra tends to inhabit the lower to middle area of the aquarium. You should also ensure that there is a close-fitting top on the aquarium because the Sailfin Tetra will otherwise probably jump out, as jumping clear of the water is in its nature – including when feeding.

The Sailfin 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. Sailfin Tetras are not a great community fish and are only ideal for aquarists with, at least, moderate experience, as they tend to have aggressive tendencies towards each other and possibly other species. Sailfin Tetras enjoy are plenty of densely clustered plants behind and amongst which they may hide.

Sailfin Tetras, like most rainforest species, prefer a shaded and well-planted tank with open areas for free-swimming, as they can hide from predation or strong light, so consider including floating leaves and/or allowing vegetation to grow so that it floats on the surface of the water to provide shade. Bearing in mind the lower pH levels preferred by Sailfin Tetras, they should be kept is an aquatic peat-filtered aquarium

It is generally advised that the minimum tank size for Sailfin Tetras should be one of 24 inches in length or more due to the shoaling nature of the species, which will enable a small (or even quite a large) 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 when the time comes for breeding.

Most (but not all) Tetras have an additional fin which identifies them as being Tetras and the Sailfin Tetra is no exception. If you look between the dorsal fin and the caudal (tail) fin of the Sailfin 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).

Sailfin Tetra – Videos

How do Sailfin Tetras breed?

Here’s the thing about breeding Sailfin Tetras…

Tetras eat their eggs and because Sailfin Tetras are no exception, they should not be left in the tank once the eggs are laid. A female will lay up to 150 eggs which, if laid in a community tank or a tank with a shoal of Sailfin Tetras in, those eggs are unlikely ever to hatch but highly likely to be eaten.

With all of the above noted then the following may be helpful for those considering breeding this unusual specimen.

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

Sailfin 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 Sailfin Tetra becomes ripe with eggs, the difference between the sexes becomes even more evident. If you plan to attempt to breed Sailfin 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, Sailfin Tetras will breed in a community tank and, if the tank is well planted, it is possible that at least a few fry may survive to reach adulthood.

Some say that a novice may find it difficult to breed Sailfin 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.

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 (though with this species, just a mature male and female is advised. She will lay her 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 150 eggs.

Spawning usually takes place in the early morning and is triggered by the rising of the sun.

Breeding tank for Sailfin Tetras

You should prepare a tank of around 10 gallons in size with mature water. The water should be at a pH of around 5.5, maintained using an aquatic peat filter and with a low level of light.

You may wish to introduce baby brine shrimp, 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 up to 150 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 twenty-four hours or so depending on tank temperature and conditions and the fry will become free-swimming after a further two to three days after hatching. Keep the tank unlit for the first week or so then gradually increase the lighting.

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

Adult Sailfin Tetras don’t need any particular inducement to breed. That said, it has been suggested that adding baby brine shrimp and 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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