Sleek, wiry, and striking: The predator catfish Aguarunichthys torosus

by Wolfgang Ros

 hat behavior could make a more sustainable impression with its owner? A medium-sized catfish with attractive colour, a slim streamlined shaped body, and a great appetite. Persistently he chases off even large adult cichlids to grab any chunks of food that is available.

Aguarunichthys torosus is an agile and fearless fighter/chaser for the “predator aquarium". In particular, the feeding time promises interesting and exciting observations. Other times it usually rests and then gives the observer the idea of a somewhat timid and pretty catfish, but with this species the first impressions can be deceptive!

The genus Aguarunichthys belongs to the family of the "Antenna Catfishes" (Pimelodidae) and includes, besides the sporadic imported A. torosus, two other species which are rare even in nature and therefore are not imported very often, A. inpai which at 42 centimeters SL is the biggest species and A. tocantinsensis which at nearly 32 centimeters SL is a bit smaller than A. torosus whose SL in nature is specified at approximately 35 centimeters. Based on a light background all three have a characteristic fine pattern of black dots/points which vary in number and size depending on the species.

Particularly striking is a light zone which is a little upstream of the middle of the body and which extends obliquely to the rear in the form of a strip from the back approximately to the beginning of the pectoral and ventral fins. Young specimens of A. torosus are more brightly coloured, but like adults they already show the typical stippling/mottling. The Latin "torosus" stands for muscular and describes the species quite well.

Kept in favourable good conditions this catfish seems to stay in good shape and does not seem to have too many grams of fat on its body, and probably why it has gained the German common name of "Stier-Antennenwels" (Bull antenna catfish).


A near adult specimen with almost 35 centimetres in total length resting on its favourite place.

A near adult specimen with almost 35 centimetres in total length resting on its favourite place

A. torosus in profile - his three pairs of highly sensitive barbels allow him excellent orientation.

A. torosus in profile - his three pairs of highly sensitive barbels allow him excellent orientation


Characteristics of Aguarunichthys torosus

Name: Aguarunichthys torosus (Stewart, 1986); „Aguarun“ = Indian tribe, which lives on both sides of the Peruvian-Ecuadorian border; gr. ichthys = "fish", lat. torosus = "muscular".

Distribution: South America (Rio Cenepa, Peru).
Size: Maximum 38 cm – 40 cm total length in nature.

Care: A little tricky only in the adaptation period, then keeping is relative unproblematic in preferably large aquariums around 24° C, a powerful filtration, weekly water change, increased current and additional air flow. Does not dig so background planting therefore is possible. Single keeping because of its intraspecies/interspecies territorial behaviour, however can be socialized well with cichlids. Predatory way of living, so do not select other fish species that are too small for sociality.

Gender differences and re-production: Unknown.

Special features: Extremely agile hunter with a good sense of smell which soon takes the food from the hand of its keeper. Also feeds on earthworms and fish fillets.

In form shape and patterning A. torosus reminds us of another, one-third bigger growing catfish of South America, namely Calophysus macropterus, which is comparatively more common in the trade. Unlike the former, A. torosus is spotted nearly to the lower side/bottom of the abdomen, it also lacks almost all of the bluish coloration which is especially characteristic for adult C. macropterus.


A. torosus looks similar to C. macropterus (right) which however is more compact and reaches a larger final length.

A. torosus looks similar to C. macropterus (bottom) which however is more compact and reaches a larger final length

Calophysus macropterus

Calophysus macropterus


Aguarunichthys torosus is not one of the fastest growing predatory catfish, although a specimen of 10 cm in length is capable in doubling its body size in about one year, after that however it needs another good two to three years to reach its maximum total length in the aquarium which is usually hardly more than 35 centimeters. Therefore A. torosus, unlike many others bigger growing Pimelodidae, can be kept well by many predatory catfish lovers.

Acquisition & Keeping Conditions
Aguarunichthys torosus is regarded as a delicate and sensitive species, especially newly imported young specimens of ten centimeters and smaller. Sometimes they can die after a short time of a mysterious skin disease which you can barely get under control with medication. Although they are much more expensive it is best to acquire animals from a length of about 20 centimeters. These should also be kept some time in the care of the dealer, so you can be quite certain that for the large price of about 100 to 150 Euros you have long lasting pleasure in your acquisition. If the catfish has been acclimatised to his new home it’s keeping turns out to be not as particularly difficult, if some fundamental indicators are respected.

With adult specimens you should not keep them in tanks smaller than a two metre length and a minimum depth of 70 centimeters. If the aquarium is too small the danger is greater that the catfish will scare itself, for example with a sudden approximation or handling in the aquarium. It can then start to abruptly dart to the surface and even jump out of the water. The temperature in the tank should be 23 to 26 degrees Celsius and the pH is ideally located between 6 to 7. Weekly partial water change is also recommended.

A good tip tip is according to their origin from a river, the species needs a lot of oxygen, so the keeper should provide for a stronger flow and additional ventilation/aeration, then the fish will feel better and visibly demonstrates this in a more active lifestyle.

Behavioural observations
Juveniles during the day like to withdraw completely into a shelter, but if the catfish exceeds 20 centimetres it does not need a shelter where it can hide completely. It will find a still viewable place in a corner in the rear area of the aquarium next to a large root or under a high solitaire plant and that is sufficient for it. There it rests during the day, most of the time.

Its urge to move around is significantly less than that of the more active C. macropterus. However if you believe, because of the reduced final length of A. torosus compared to C. macropterus, to be able to fall back on a smaller tank you will be soon taught a lesson after introducing this catfish in the aquarium. Though the movements of C. macropterus sometimes can be quite fast, A. torosus once it picks up speed is striking in its motion sequences which is fast paced and like lightening. When fed also during the day, otherwise no later than the onset of darkness, this catfish leaves its place immediately and is actively looking for food. Younger specimens no longer stay in their hiding places and they begin to roam widely in the tank.


A. torosus at full throttle.


This species is not a digger so that planting is possible with robust bigger growing plants. Aguarunichthys torosus is a predatory catfish which likes devouring live food such as earth worms, but it also eats frozen foods such as whole and unbroken smelts, shrimp or mussel meat. After a short familiarization phase it does not disdain from eating fish fillets. Juvenile catfish can be accustomed early to compound and mixed feeds such as tablets or pellets, adult specimens however take them reluctantly.

This species will gladly prey on smaller fish. Their hunting behaviour is interesting, which I could observe well after a feeding of a large number of young, only a few centimetres large, Archocentrus nigrofasciatus. Thereby it became clear how very quickly this predator catfish is able to lunge out. Although the young cichlids felt safe in a protected corner specially set up with roots and large stones, my 35 centimetres in total length, nearly adult A. torosus, registered them immediately, as his barbels slightly moving in their direction told. Apparently he was only waiting for a switching off of the aquarium lighting, and indeed, even with the room lights switched on, he preyed on them. Firstly he scared the cichlids by restless searching movements, after which they sought salvation on a wild run. He surprised them by a sudden, rapid lunge, and having had devoured seven cichlids the catfish went to his favourite place near a larger root and stayed motionless all during the night.

Skilled food thieves
Aguarunichthys torosus also likes to show his ability in a completely other kind of hunting, namely when it comes to snatching other predators food or prey. He demonstrates this behaviour above all when he is getting a raw deal with feeding and the associated fish, because of the size of the food offered and the time needed to devour it completely. Then the hunting instinct of the catfish awakes and he gets carried away with ever more daring actions. He will even steal from adult Astronotus ocellatus any morsel of food such as fish fillet, even if it sticks out just a little bit out of their mouth. Persistently A. torosus will pursues the cichlids and in doing so his extraordinary agility benefits him. Every direction the beleaguered cichlids will take he manages to keep almost direct body contact and harass them further in turbulent movements until it provides a way for him to pull the piece of food as quick as a flash from the mouth, or at least tear or rip off a part of it. If A. torosus has the opportunity to eat himself full, the need and requirment which with many other predatory catfish can be observed, namely to eat very next day again if the opportunity arose, is low. With him two or three days may pass in which he downright scorns further food. For adult specimens therefore a feeding of twice a week is absolutely sufficient.

Territorial behavior
With conspecifics and other species A. torosus behaves fairly territorial, although you can still keep together juvenile catfish if the aquarium provides enough hiding places but with adult animals this does not work normally. They are too much of a loner, and their territories, which they claim against other species are too large, and that usually includes the entire tank. At best large public aquariums permit such a coexistence. Opposite to other fish species the territory is not so much pronounced. An adult Aguarunichthys only defines its territory area about 30 centimeters around his usual place, but this zone he then defends against much larger fish being quite aggressive and resolute. Usually A. torosus in the context of its defensive action succeeds to catch the intruders by fast and agile movements on very exposed body areas like the tail fin with its mouth and pinching them in repeated attacks for so long until they take flight. The socialised fish will soon have learned to keep well away from this territory and so in sufficiently spacious tanks socialisation for example with cichlids is possible. Even with larger cichlids the keeper does not have to worry about the well being of his A. torosus because he shows himself surprisingly assertive, especially at night where he will he wander around the entire bottom of the tank. The cichlids know that and will only remain in the middle and upper water regions.

At this stage however it can come to conflicts with other bottom oriented predator catfish. A. torosus tries to impress mainly through bumping, so I could not watch injuries caused from that, so usually my specimen, which is socialised with several Pimelodus ornatus and Exallodontus aguanai will strike out blows as fast as lightning. They have become used to his attacks long ago and they normally avoid them. So if you want to socialise A. torosus with other predatory catfish one should fall back on smaller, fast swimming, and especially agile species and provide them with additional retreats if at all possible. One should avoid keeping this species together with larger and territorial species from the Pimelodidae or Pseudopimelodidae, otherwise trouble will be inevitable. In addition the keeper should always be aware of the fact that A. torosus is a predator catfish and for him, too small a fish, and these are basically all which have less than a third of his own body size, especially over night, run the risk of being eaten.


A.torosus with Astronotus ocellatus

A.torosus with Astronotus ocellatus

A.torosus with Pimelodus ornatus and Exallodontus aguanai

A.torosus with Pimelodus ornatus

A. torosus knows itself well enough to be able win through in a community tank with cichlids and other predatory catfish


The behavior towards the keeper are clearly different from C. macropterus that even after many years remains a bit cautious. Although initially it lives very withdrawn sometimes even adult specimens lose their shyness and even take food from the hand. The high speed which they show thereby is unusual for predatory catfish. Resting on the ground my specimen has already, after a short time sniffing the scents and the trace smell from the dipped fish-pieces, takes a few lines on the ground restlessly and finally ascends in searching movements. His two longest barbles in these moments literally vibrate and making as good a location as possible, he single mindedly moves to the surface of the water where the fish pieces have been immersed. Swimming by then he pulls and tears larger pieces abruptly, and if necessary with pressure, and forces the chunks out of my fingers which then at once disappear in the surprisingly wide open mouth. Finally the catfish submerges, goes to his favourite place only for a moment and then returns taking the next chunk out of my hand.

The following images shows these motions.



Tame to the hand A. torosus, which grabs the the piece of fish fillet at first very quickly and then completely snatches it away from the hand with a strong shaking motion.

Tame to the hand A. torosus, which grabs the the piece of fish fillet at first very quickly and then completely snatches it away from the hand with a strong shaking motion.

Tame to the hand A. torosus, which grabs the the piece of fish fillet at first very quickly and then completely snatches it away from the hand with a strong shaking motion.

Tame to the hand A. torosus, which grabs the the piece of fish fillet at first very quickly and then completely snatches it away from the hand with a strong shaking motion.

Tame to the hand A. torosus, which grabs the the piece of fish fillet at first very quickly and then completely snatches it away from the hand with a strong shaking motion


My overall impressions of A. torosus is that it just looks great. This catfish impresses with its elegance of its body shape, markings and swimming movements. As a powerhouse he knows to win through even in a predatory community. The experienced lover of predator catfish will not be able to avoid this species and should not be deterred by the relatively high price, if he/she can find it on the list of catfish specialist retailers.




This article was published in July 2010 in the German publication: "Die Aquarien und Terrarienzeitschrift" (Datz) 63 (7): 26-29. My thanks apply here to the Datz editorship and their editor-in-chief, Rainer Stawikowski, who gave me kind permission to publish this article on ScotCat.



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