Book Review: Corydoras: The most popular armoured catfishes of South America

This is a review of the new CAS library book Corydoras: The most popular armoured catfishes of South America, by Werner Seuβ (1993). This book was purchased for the CAS library with financing from a special auction of Corydoras catfishes donated by CAS members Birgit McKinnon and Gernot Kostera.

Dr. Seuβ (pronounced soos: don’t laugh) is an avid aquarist, and he has raised almost the entire Corydoras species flock in his own home in Sparneck, Germany. Since the publication of this book he has also had a fish named after him; Corydoras seussi. Too bad that this fish was described too late to be included.

This is a fabulous book.

All 128 Corydoras species known in 1993 are in the book; and all of them are presented with description, a location map, and a pen-and-ink drawing; and almost all of them with a color photograph as well.

And the photography is the best I have ever seen in any publication other than National Geographic. Each picture shows the fish clearly and with exquisite sharpness in a beautifully planted tank. Not a blemish or any hint of grain is found is any of the photographs. Yet each photo has soft natural light that does not reveal any clue as to what lighting was used. It is however obvious that the subjects were at least partially fore-lit as the reflective iridescence of the scales is clearly seen. No better photographs of aquarium fish will ever be published (the photograph of the two Corydoras “C5” is particularly wonderful). Unfortunately, the book make no mention of what camera, film, or lights were used; only that the photographs were “from a collection of many thousands of slides”.

The book also has pen-and-ink drawings of each fish by Jürgen Härtl. These are also of the very highest quality.

As far as the other technical aspects of the book’s production goes, it is your typically German over-engineered artifact that uses the highest quality paper and bindings.

The book was translated from German by Klaus Berold and Bernard Michaelis, who did an outstanding job. The grammar of the translation is impeccable. Their only lapse is the retention of the single German word “Fundorte” in the map foldout. And of course the proper German spelling of “Seuβ” is retained, rather than the commonly seen translation “Seuss”.

The book uses metric units throughout, except that the German degrees of hardness are used (these can be converted to PPM by multiplication by 17.9). The spelling convention used in the translation is British, which has the annoying affect that temperatures are written with the redundant ” º ” symbol, as in “27 º C”, rather than the scientific standard “27C”. Another minor annoyance is that Corydoras, although always capitalized, is not italicized when it is used outside of a complete scientific name (and unfortunately one or two scientific names didn’t get italicized either).

The final comment about the book’s production is that this is neither a readily available nor inexpensive book. Despite extensive searches, I have yet to find a Canadian supplier. It can however be ordered over the Internet from the States. Try the Aquatic Bookshop ( who have it in stock for US$67.44. Or else try Amazon ( who can get the book for US$49.10, but only on special order (4 to 6 week before shipping). You can pretty much double those prices once you pay for shipping, currency exchange, and GST.

The book opens with a brief presentation of the classification of the Corydoras, as members of the subfamily Corydoradinae, of the family Callicthyidae, of the order Siluriformes.

The Corydoras share their subfamily with the genera Aspidoras and Brochis. It is stated that Brochis can be told from Corydoras by the larger number of dorsal rays in Brochis: 10 to 17 rather than the 6 to 8 in Corydoras. Aspidoras is however more difficult to identify; as they have the same number of dorsal rays as Corydoras, but tend to be smaller and more elongated than the typical Corydoras. Aspidoras do however have a dual fontanel (defined as an “opening in the headbone”) while Corydoras and Brochis have a single fontanel. This is of no use in identifying living specimens however.

I think it is a shame that the book is restricted to detailed descriptions of only the Corydoras species, and leaves out Aspidoras and Brochis. The entire subfamily Corydoradinae could have been covered with relatively little additional effort, given that Brochis and Aspidoras have so few species. Why not include the two related genera in a future edition?

The housing of Corydoras in the community aquarium is discussed in the second chapter. It is recommended that at least 6 to 8 of each species be kept together in a tank. The practice of keeping Corydoras in pairs or in mixed-species schools is discouraged. A substrate of well-rounded gravel is suggested. The tank should be planted and supplied with caves. The recommended water chemistry is not very restrictive: a pH of 6.5 to 7.5 and a hardness up to 270 PPM CaCO3 is recommended (by these criteria Calgary’s water is too alkaline by 0.5 points but has an OK hardness). Temperatures in the range of 22C to 28C are advised. The need to feed the Corydoras properly is also stressed: do not rely on them scavenging the other fishes’ leftovers; feed them sinking food tablets, thawed frozen foods, or live foods.

Seuβ cautions against the use of several common aquarium medications, as these are detrimental to catfish. He also states that "Even though I have used many types of medications I have barely been able to save diseased Corydoras“: an experience repeated by aquarists all over the world who have wasted their money on over-the-counter fish medicines. It is always better to maintain fish properly, thus preventing diseases from occurring in the first place, than trying to cure a diseased animal.

The breeding of Corydoras is discussed next. While some Corydoras spawn readily in the aquarium, others have proven difficult. Seuβ has bred more than 30 Corydoras species, but there are still some that continue to frustrate.

Seuβ uses 45-liter breeding tanks with a thin (2 to 3 mm) layer of fine gravel on the bottom, some plants (usually Anubias), a few hiding places, and a fairly powerful outside power filter. He also keeps a Sturisoma species catfish in the breeding tank for algae cleaning duties (apparently they won’t eat the Corydoras eggs).

His breeding hints include instructions on how to catch a catfish in a display aquarium: don’t feed for two days then put a couple of food tablets in a net propped up inside the aquarium. Be patient and the catfish will (eventually) find their way inside the net.

Once the catfish are caught, they must be sexed: male Corydoras have much more pointed anal fins than females.

The prospective parents are transferred to the breeding tank, where they are fed heavily on live foods. White worms, Grindal worms, and Tubifex worms are choice foods (the thinness of the sand layer is to prevent the worms from burying themselves out of the catfish’s reach). Mosquito larvae are also recommended as food.

To stimulate breeding, Seuβ recommends a change of water every two days with fresh water that is slightly cooler than the tank, and a drop in temperature of 4C at night. Lower the pH with peat filtration, and provide a stronger current. Changing the fish’s diet and/or the location of the tank to a brighter location may also help. Oddly, he also recommends placing “dried seed-free alder cones” in the tank, but does not mention their intended purpose (pH reduction?).

Courtship is initiated by the male, who swims around in a nervous fashion agitating the female. Pairing begins when the female stops avoiding the male and remains stationary at the bottom of the tank, making only small movements. The male will position himself cross-wise in front of the female in the “T-position”. The female then releases eggs into her ventral fins, which she cups into a basket to carry them. The eggs are fertilized by the male while in the basket. The female then carries the eggs to be deposited at a suitable site, usually a plant leaf. Seuβ recommends Anubias plants as suitable eggs sites, as they are tough enough to withstand the abuse.

The plant with the eggs is then transferred to a 20-liter bare-bottomed hatching tank, to which the anti-fungus medication CILEX is added. The hatching tank is kept aerated and filtered with a sponge filter. Temperature s kept at a relatively low 23C or 24C, as it is stated that the lower temperature results in lower mortality. The tank bottom is to be kept clean with a brush.

Unfertilized and fungused eggs are removed as they are noticed. Two or three days post hatching feeding is begun: newly hatched brine shrimp are fed to all except the fry of the smallest Corydoras species, which require infusoria.

The fry are transferred to rearing tanks when they outgrow their hatching tank. A thin sand substrate is recommended since Seuβ finds that bare-bottomed tanks, unless kept scrupulously clean, result in fungus attacking the ventral fins and barbels. A powerful filter is also advised. And finally, it is suggested that the young fry be sorted for size every couple of weeks, or the smaller fish will never attain their full size.

The chapter of breeding advice is followed by a table of 28 representative species, and for each lists the desired sex ratio, temperature, size of eggs, hatching time, time of first feeding, suitable first food, total number of eggs laid, and the number of eggs carried by the female at any given trip in her ventral fin basket. The last entry I found most surprising, since most Corydoras females only carry 1 or 2 eggs at a time, but a few species really load up, with as much as 25 eggs in the case of Corydoras elegans.

The remainder of the book contains detailed descriptions of 128 scientifically described species of Corydoras, with three of these species having separate entries for their identified subspecies. There is additional entries for 17 undescribed species identified by their “C numbers”, 1 through 17. Each description includes a detailed line drawing, a textual description of the appearance with pointers on how to distinguish the fish from similar species, and a location map of the place the fish is found in nature. Most descriptions also have a color photograph.

All Corydoras aficionados need this book. It is simply the best book on any genus of aquarium fishes available, and it would be the constant companion for anyone wishing to begin breeding a representative collection of these fishes. My only serious concern is that, with a publication date of 1993, the book is already getting old. Many new species of Corydoras have been properly described since the publication of this book, and a second edition would be greatly welcome.


Seuβ, W. 1993. Corydoras: The most popular armoured catfishes of South America, Dähne Verlag, Ettinglen, ISBN 3-921684-18-8 ?