Austrolebias monstrosus, (Huber, 1995)


The type locality of Austrolebias monstrosus is near La Serena, Boqueron Department, Paraguay. First discovery was on March 21, 1950 by S. Pierotti. Later the species was rediscovered by Dan and Pat Fromm on October 10, 1992. On March 15, 1994 it was collected again by the dutch Leen & Arjan van den Berg.

It was originally described by Dr. Jean Huber as Cynolebias monstrosus but was transferred to Austrolebias by Costa (1998) as he erected this genus.

The name monstrosus is given in reference to its morphology and its cannibalistic behaviour to smaller fishes in its enviorment, especially to the other annuals.

Costa placed this species with others in the genus Megalebias (but as turned out this was not a good decision he placed them back in the genus Austrolebias during 2001.

Close relatives from Austrolebias monstrosus are A. elongatus and A. prognathus. These fishes are seldom seen in the hobby as they requier big tanks, lot of food and special breeding skills.

Austrolebias monstrosus. - male. Santa Maria, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.
Austrolebias monstrosus - pair. Santa Maria, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.
Austrolebias monstrosus - detail head. Santa Maria, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.


To breed most Austrolebias you need a tank that has about 10 to 25 litre water in it, a small jar or plastic container of about 10 to 15 cm high , a little bit of well boiled peatmoss or coco-peat and a watertemperature between 18 and 24 C. It is wise to add an small filter to that tank and change water on a regularly weekly basis for 90 %. Bring 1 male and, if possible, 2 or more females in the tank and feed the fishes daily with life food like daphnia, red- and black mosquito larvae and white worms. Austrolebias does not accept dry food easily and also heart is not taken if other live food is offered. If possible breed this genus in bigger tanks with more than one pair or trio and give some hiding places if you do so. In case of breeding with more than one male you also should provide more than one spawning container. Every male must have one and you will see they show nice territorial behaviour to attract females into there own spawning place.

The male flinders around the female, displaying his fins high- up with most intense colours. As the female is willing to spawn she follows the male that is pressing his head towards the layer of peat and as the female contact the belly of the male both of them dive into the peat layer. This layer should have a thickness of at least the length of the biggest animal or better some deeper so they can dive completely into it.

The spawning take place during the whole fertile life of the fishes, starting at 5 to 6 weeks of age till they become old and weak or die by the lack of water in there natural environment. This will be within 8 to 11 months, depending on the temperature . Higher temperatures will trigger more rapid aging. In the wild Austrolebias lives in cool environments during the wintertime. Temperatures in Uruguay, Paraguay and Argentina can get very low. Incubation time is normally 6 weeks if stored at high temperatures ( 25 C.) and longer if kept at lower temperatures. The development can take that 5 tot 6 months also. So it is wise to check the eggs on a regularly basis to see if the eyes inside the eggs are fully developed and the iris is good visible. If eyed- up, put a part of the peat with the eggs in water that has an cool (ca. 18 C) temperature. If the fry hatches normally and swim within a few hours you also wet the rest of the peat. After hatching I feed the fry immediately with Artemia nauplii.

A day or so later I pour the water together with the fry off and place them in well filtered tank without any peatmoss to grow up. Austrolebias are not used to strong currents and juveniles can die if turbulece is to strong.The remaining peat will still have eggs inside that are not ready to hatch. You can repack the peat and store it for some extra time. This is nature's answer on short rain showers that fill pools only temporarily followed by another dry period. Such an event would kill the complete population of the species in that area if all eggs would have hatched with first rains. These (late) eggs will hatch later, sometimes very much later, and the older ones will eat these youngs.

As stated before, young’s are growing fast and will produce their first eggs after 5 to 6 weeks already, if not even sooner. This breeding information is applicable to most Austrolebias. If the above Austrolebias- species do have an different behaviour you will find below in this chapter under <remarks>.

Jorge Stojan wrote:

The biotope of Austrolebias monstrosus "Santa Maria, KCA 75/08" is situated in the province of Salta, Northern Argentina. It is a very dangerous place to go and the most northern record in Argentina. In this biotope the following species live together: Austrolebias monstrosus, Austrolebias vandenbergi, Papiliolebias bitteri, Trionectes aplocheiloides, and Neofundulus paraguayensis. The maximum depth of 1.70 meters was there, PH 7.

Reproduction in aquarium is not easy because the male can grow up to about 17 cm, and the pair need a deep layer of peat that is constantly spread around by the strong movements of fish. The incubation of their eggs is 12 weeks at approximately 25 ° C.


Be aware.... Austrolebias monstrosus is a predetor on smaller fish, also the youngster's that are growing less rapid become food for the bigger ones. Mostly those are the females so males only remain if no action is taken by the breeder. Separate the faster growing fishes directly from the smaller ones is the advise. The use of a breeding container with the entrance- opening at the side can become handy as the fish will not propell all the peatmoss out of the upper opening during the dive.

Biotope of Austrolebias monstrosus. Santa Maria, Nothern Argentina, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.


Max. size 15.0 cm.
Dorsal 17.0,
Anal 22.0,
D/A 7.0
LL scale count (average) 69.6
Pre- dorsal length to % SL – 69.3 %
Depth to % SL – 28.6 %


Huber, J. H. 1995. Nouvelles Collections de Cyprinodones paraguayens, avec Description de 4 Especes Rivulines inedites et Redecouverte d'une Espece a la Localite typique jusqu'alors indeterminee. Assoc. Killliphile Francophone de Belgique, Killi Contact, Aug. 23 (2): 9, fig. 4.