Chris Ralph


here are numerous species of Corydoras available to the hobbyist, many of which have been described for years, some of which have only recently been discovered and are awaiting identification and subsequent naming. I think that this is something which will always fascinate me, the fact that there are new species potentially awaiting discovery from remote corners of the South American continent.

The thing that concerns me personally however, is the rate at which the rain forests are disappearing, which not only impacts upon the natural habitats of these wonderful catfish and the associated other forms of fauna and flora, but also upon us the human population as well. With all the doom and gloom surrounding climate change I wonder how long it will be before the situation reaches its conclusion, and where all life will feature? As many of you are aware I have been fortunate enough to visit the Amazon and some of its many tributaries in order to observe some of our aquarium fishes natural habitats, which will form part of some future articles.

It is my intention to cover some of the often overlooked species of Corydoras - the ‘dwarf’ or ‘pygmies’ as many aquarists refer to them as. I have kept many species of Corydoras and to this day still find them very fascinating to watch and observe. As you are most likely aware Corydoras belong to the family Callichthyidae, sub-family Callichthyinae, which also includes the genera Aspidoras, Brochis, Dianema, Hoplosternum, Lepthoplosternum, Megalechis and Scleromystax, and just to keep us on our toes the taxonomists like to cause more confusion when they review the families as has happened during recent years. This has resulted in some species of Corydoras being reclassified as Scleromystax. I guess that it is this confusion within taxonomy, as well as the observations made over many years which makes this family of catfish so interesting and fascinating to keep.

When keeping these catfish the following information might be of use especially to those of you venturing into keeping Corydoras for the first time:

Water parameters – Corydoras prefer to be kept in water which has a pH in the range of 6.0-7.2, and hardness in the range of 2-25°dGH. This catfish is ideally suited to temperatures in the range of 23-27ºC or 73-81ºF.
Feeding – As with all the other catfish that I have had the pleasure to keep over the years, Corydoras readily accepts a mixed and varied diet which includes granular foods, frozen bloodworm and good quality flake to name but a few. Due to the relatively small size of these catfish I would suggest that the dry foods offered are slightly crushed to make them smaller for these fish to eat.
Aquarium size – I would suggest a minimum size of 18” x 12” x 12” or 24” x 15” X 12” for a small shoal of these catfish, with plenty of hiding places amongst bogwood and rocks. These magnificent tiny catfish might also be suitable for adding to a ‘Nano’ type aquarium in smaller numbers. The ideal aquarium substrate to use with these catfish is aquarium sand such as BD Aquarium Sand. As with all other species of fish, water quality and general husbandry is very important, and I would recommend that a minimum of 25% water is changed on a weekly basis.
Compatibility –Wherever possible I would recommend that the aquarist keep these catfish in a community aquarium in small groups of six or more, but as the absolute minimum I would suggest three specimens. In their natural habitat Corydoras would be found in relatively large shoals.
Sexual differences – The males tend to be more slender than the females.
Breeding – There are numerous documented reports of aquarium spawnings of Corydoras. The majority of Corydoras adopt the typical “T shape” breeding clinch when spawning. The spawning activity follows on from a period of conditioning with foods such as Daphnia and bloodworm, and a partial water change using cooler water, which replicates the lead up to the rainy season in their natural habitats – the trigger for breeding activity to take place.

For the purpose of this article I have documented four species of Corydoras which do not attain lengths above 40mm standard length which is the measurement from the tip of the snout to the base of the caudal peduncle. All sizes quoted are in mm standard length.

Corydoras pygmaeus – Knaack, 1966
Common Name – Pygmy Cory
Natural Habitat – South America namely Brazil, Est. Rondônia, surroundings of Calama, along Rio Madeira near the mouth of Rio Jipiraná (Rio Machado). Also found in Ecuador, Napo Province, Rio Aguarico, Peru, Loreto Province, and Rio Nanay near Iquitos.
Size – Males 25mm & females 32mm
Body – Typical triangular body shape with the head being short and compact.
Colour – Base colour of head and body grey/green. Blackish coloured line running from the tip of the snout through the junction of the body scutes ending at the caudal peduncle, where it broadens out into a triangular shape. Dorsal parts of dorsolateral body scutes with darker pigment on the posterior edges. Ventrolateral body scutes are creamy white with the exception of a dark line which runs from the ventral fins to the anal fin. All fins are described as being clear.
Remarks – This species is often mistaken for Corydoras hastatus within the aquatic trade. Corydoras pygmaeus lacks the lozenge-shaped blotch at the root of the tail along with the white to yellowish coloured margin above and below. This species sports a black band that runs the full length of the body, ending just short of the tail end, and ending in a slightly broader band when compared to Corydoras hastatus.
Etymology – Cory meaning helmeted, doras meaning leathery skin (helmeted Doras) cuirass. Pygmaeus from Latin meaning dwarf.

Corydoras hastatus – Eigenmann & Eigenmann, 1888
Common Name – Dainty Corydoras
Natural Habitat – South America namely Brazil, Est. Amazonas, Villa Bella, Parintins. It is suggested that this locality is doubtful as there are several Villa Bellas (Vila Bela) in Brazil and the species is common within the Rio Paraguay drainage in Brazil and Paraguay
Size – Males 25mm & females 32mm
Body – Typical triangular body shape with the head being short and compact. The dorsal fin has 1 hard ray and 7 soft rays. The anal fin has 2 hard rays and 5-6 soft rays. There are 22 bony scutes in the upper lateral series and 20 in the lower lateral series.
Colour – The base colour of the body and head is grey-green to golden yellow. The back is olive green; the flanks are yellowish with a whitish coloured belly. The head, body and fins are sprinkled with small dark spots. A black longitudinal band runs from behind the gill cover to a lozenge-shaped blotch at the root of the tail; the latter blotch having a white to yellowish coloured margin above and below. A second broader streak runs along the lower edge of the caudal peduncle. The fins are dull grey. The base of the caudal fin is blackish in colour.
Remarks – This species is said to prefer a specific habitat which is called the ‘swimming meadows’ of the Pantanal and Choco region. In its natural habitat this catfish is generally found in small groups of 15-20 specimens. There is a characin – Serrapinnus kriegi which closely resembles this catfish and is often found in amongst shoals of the catfish. This is a very small mid-water shoaling species, which does not spend as much time on the substrate as other species do, preferring to sit on the leaves of aquarium plants rather than sitting on the substrate.
Etymology – Cory meaning helmeted, doras meaning leathery skin (helmeted Doras) cuirass. Hastatus from Latin meaning armed with a spear.

Corydoras habrosus – Weitzman, 1960
Common Name – Dwarf Corydoras
Natural Habitat – South America namely Venezuela, State of Cojedes, Rio Salinas, tributary of Rio Pajo Viejo, El Baúl.
Size – Males 32mm & females 35mm
Body – Typical triangular body shape with the head being short and compact. The dorsal fin has 1 hard ray and 7 soft rays.
Colour – Base colour of head and body pale tan. There are three dark blotches along the middle of the body, the first below the dorsal fin, the second between the dorsal and adipose fins; the third and darkest blotch is on the caudal peduncle. The three azygous scutes before the adipose fin have dark pigment on them. There is scattered dark pigment on the dorsolateral body scutes, the ventrolateral body scutes are without pigment except for the upper portions of those scutes associated with the three dark midside blotches. The dorsal fin is clear except for two dark rows of fine spots. The adipose fin membrane is clear with some dark pigment on the spine. The caudal fin has four light rows of spots in the upper lobe and three in the bottom lobe. The pectoral, ventral and anal fins are clear.
Remarks – Some older aquatic literature refers to this species as Corydoras cochui, sharing a similar colour pattern. Corydoras cochui has a more slender body than Corydoras habrosus and one more blotch on the side of the body. Corydoras habrosus has no spot at the base of the ventral fin, and the pectoral fins are not barred.
Etymology – Cory meaning helmeted, doras meaning leathery skin (helmeted Doras) cuirass. Habros from Greek meaning pretty, delicate or dainty.

Corydoras cochui – Myers & Weitzman, 1954
Common Name – Pygmy Catfish, C022, Barred-tail Corydoras, Cochu’s Catfish.
Natural Habitat – South America namely Brazil in the Upper Araguaia River basin. Also documented as being found in the Rio Araguaia, Santa Maria Nova and State of Goyaz (Goiaz).
Size – Males 30mm & females 35mm
Body – Slender with a rounded snout, although it does still have the typical triangular appearance which makes this family distinct.
Colour – Base colour of body and head is light brown. There are four dark coloured blotches along the flanks; one below the dorsal fin, one between the dorsal and adipose fin, one below the adipose fin and one on the caudal peduncle. There is a dark streak along the back of the fish which extends from below the dorsal fins spine, ending in a dark spot on the upper edge of the caudal peduncle. The top of the head is dark in colour which continues just below the eye. The upper and anterior portion of the opercle is also dark in colour. The caudal fin has five narrow irregular dark coloured cross bands. The base of the anal fin has a dark coloured spot extending into the body. Ventral fin is clear. Pectoral fin rays with a few dark coloured scattered spots. Dorsal fin rays with a scattering of dark coloured spots forming two irregular rows. Dorsal and pectoral fin spines having a narrow dark line along them.
Remarks – This particular species is not commonly available, but is well worth looking out for and is ideal for smaller aquariums.
Etymology – Cory meaning helmeted, doras meaning leathery skin (helmeted Doras) cuirass. Cochui named in honour of Mr Fred Cochu.

In addition to those species detailed above the excellent book - Identifying Corydoradinae Catfish by Ian Fuller and Hans-Georg Evers mentions the following two species, which to date I have not had the pleasure to see for sale:
Corydoras paragua - Knaack, 2004. A species from Bolivia. Males attain a length of 35mm, and females 40mm.
Corydoras multimaculatus - Steindachner, 1907. A species from Brazil. Males attain a length of 35mm, and females 40mm.

The next time you are looking to purchase some smaller fish spare a thought for these miniature catfish, you will not be disappointed!

Glossary of terms:

Caudal is defined as the tail fin. Pectoral fins are defined as paired lateral fins. Dorsal fin is defined as the medial fin on top of the back. Adipose is defined as a second dorsal fin which in the case of Corydoras consists of fatty tissue with a single spine supporting a thin membrane. Dorsal is defined as being top or above. Ventral is defined as bottom, below or underneath. Opercle is defined as the large bone forming the gill cover. Caudal peduncle is defined as the usually narrowing posterior part of the body between the anal and caudal fins. Scute is defined as a bony plate. Dorsolateral is defined as extending from the top to the side. Ventrolateral is defined as extending from below and to the side.

References:

Catfish Association Great Britain – Volume 1
Catfish Association Great Britain – Information Book 6
Identifying Corydoradinae Catfish – Ian Fuller & Hans-Georg Evers
www.scotcat.com
www.fishbase.org
www.planetcatfish.com

All Image's by Author apart from Corydoras cochui which is credited to Ian Fuller of www.corydorasworld.com