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Semaprochilodus insignis

Flagtail Prochilodus




Native to Ecuador, Peru, Colombia, Guyana and Brazil.


It migrates and spawns in the river channels but feeds mostly in the floodplains. It can also be found in floodplain lakes (known locally as “várzeas”) and forest streams.

Maximum Standard Length

Around 14″ (35cm).

Aquarium SizeTop ↑

An adult specimen will need a tank measuring at least 60″ x 24″ x 24″ (150cm x 60cm x 60cm) – 540 litres.


This species is quite unfussy regarding decor, but if you want to keep it in natural surroundings a biotope setup would be very simple to arrange. Use a substrate of river sand and add a few driftwood branches (if you can’t find driftwood of the desired shape, common beech is safe to use if thoroughly dried and stripped of bark) and twisted roots. Algal growth should not be discouraged as the fish will graze on it. It’s not the best choice for a planted tank, as it will devour any soft-leaved species and even less palatable vegetation will probably be picked at.

Water Conditions

Temperature: 73 – 84°F (23 – 29°C)

pH: 5.5 – 7.2

Hardness: 1 – 15°H


Though omnivorous it’s primarily a herbivore. Offer plenty of vegetable matter in the form of blanched spinach, lettuce, cucumber, courgette, algae wafers and similar. It will also accept most good quality dried foods and small frozen fare such as bloodworm or [Daphnia.

Behaviour and CompatibilityTop ↑

It’s aggressive towards its own kind when kept in small numbers, but can be maintained in groups of six or more in larger tanks. Otherwise it’s best kept as a single specimen in a community of medium to large fish. Suitable tankmates include other large characins, Loricariids, Doradids, peaceful cichlids, knifefish, arowana and freshwater stingrays.

Sexual Dimorphism

Difficult to sex, although mature females are said to be rounder-bellied than males.


Unrecorded in the hobby. The species has a complicated migratory spawning cycle in nature (see below).

NotesTop ↑

Semaprochilodus are one of the most common and widespread shoaling fish found in South America. Over a dozen species have been described but most are never imported. They are used as food fish in their native countries. It makes a stunning addition to a community of larger fish.

Along with some congeners, S. insignis is commonly known as the Jaraqui in Brazil. It is an interesting species both ecologically and biologically. In nature it migrates over large distances in huge shoals according to the season, feeding on organic detritus. This detritivorous feeding habit and migratory nature plays an important part in maintaining ecosystem structure and dynamics as it processes large amounts of organic sediments as it sifts for food. It also has two stomachs, one of which is filled with mud to aid digestion.

It migrates twice a year. The first event is a spawning migration at the start of the wet season, when the fish move from nutrient-poor black and clear water tributaries and streams into the more turbulent white (silt-laden) waters near the heads of rivers to spawn. They may travel several hundred kilometres and can even be seen leaping through rapids in a similar fashion to salmon. Post-spawning the fertilised eggs drift downstream and into the nutrient rich floodplains. These act as the perfect “nurseries” for the fry to feed and grow.

The adults meanwhile return to exactly the same flooded forest tributary from where they came to feed for the next 3-4 months. They then migrate again in the middle of the wet season, moving once more from the tributaries upstream into the nutrient-rich rivers, where they may enter many different tributaries. They continue this activity until the water level drops. When it rises once more the fish spawn again in the mouth of the tributary they are currently in.

Interestingly it appears that older fish do not undertake these migrations, as reported by Ribeiro and Petrere (1990). They did not suggest an age limit for migration but did note that non-migratory fish were much larger than the migrating individuals and tend to occur further up the tributaries.

It can be distinguished from the other commonly-imported species, S. taeniurus by the fact that the dark spots present on the flanks of juvenile specimens fade as the fish matures. In S. taeniurus these remain throughout the fishes’ life.

One Response to “Semaprochilodus insignis (Flagtail Prochilodus)”

  • Hamish

    Hi there,

    These are great fish, but I was just wanting to check some thing…Does the Insignis also have red fins or is it only the taeniurus ? There are “Flagtail Prochilodus” for sale in my LFS but they all have red fins so I just wanted to check.
    Many thanks.

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