They are entirely peaceful, never known to nip fins. Their body armour keeps many diseases and parasites at bay. They will not eat or pull up plants. They do not rearrange the substrate. They accept pretty well any regular fish food. They very rarely jump out of the aquarium. Their body pattern designs of spot, lines, squiggles, eye masks, saddles, and more, are works of nature’s art. Although mostly lacking any bright colours, metallic sheens glint as they catch the light. They clean up other’s left-overs, and till the substrate simultaneously. There are tiny species through all sizes to big ones. Some are easy to captive breed, many more are breedable. Almost all are undemanding to keep. Ideal aquarium fish!
Well, what are they? They are the Armoured Catfish of the subfamily Corydoradinae. Three genera are in discussion here. Aspidoras, Brochis, and Corydoras. Just how many species are now known to the fishkeeping hobby is almost impossible to determine with so many new species and types coming to light with each new area opened up for collections. They are confined to South America, including some offshore islands. There is well in excess of 120 named species, and others which are either new species or regional varieties of named species yet to be determined. It hardly matters to the fishkeeper what the differences are between the genera, as their behaviour and modest requirements are in accord. However, basically the difference between the Brazilian Aspidoras and their so-similar Corydoras cousins is the opening in the head bone (fontanal) which is double in the Aspidoras and single in Corydoras. The Aspidoras species have somewhat elongated bodies compared to the majority of Corys. The Brochis genus differs from both Aspidoras and Corydoras by having a greater number of fin rays. The Brochis can have as many as 17 dorsal fin rays whereas the Aspidoras and Corydoras can have as few as 6 and not more than 8. Collectively the three genera are known as Armoured Catfish, and more popularly as “corys”.
All three genera sport an adipose fin, set well back from the dorsal fin and close to the caudal peduncle. The caudal tail fin is forked – often quite markedly so, or may be gently crescent-shaped, and anywhere between the two extremes. Careless handling of a netted specimen can be a painful experience as the dorsal and pectoral fins have pointed spines reinforcing their structure. If the skin is punctured by one or more of these spines a sharp stinging sensation ensues, usually attended by some swelling and flaring up of the wounded area. (If there has to be a down side to these species maybe this is it, but it will only happen as a result of carelessness!).
The barbels, or “whiskers”, are a notable feature of these interesting fish. The downturned mouth is obviously designed for bottom feeding, and the stout nose carries an array of barbels. With such well equipped snouts they are able to dig into the soft substrate and winkle out tasty worms and crustacea with ease in their natural habitats. Regular aquarium substrates are generally composed of grains of about 1/8th” or more which is fine for most other fish and plants. But this gravel is hard on the grubbing catfish as they purposefully poke into its uninviting surface. A thoughtful approach is to provide a patch of soft sand for them to rejoice in as a relief from the gravel. This facility may be made into an attractive feature of the aquarium decor. A pebble or rocky border is needed to keep the sand from mixing with the surrounding gravel, and shaped to form a “pathway” leading the eye from the front area of the tank, through the plants, disappearing into the void at the back of the aquascape. Imagination is all that is needed to expand this idea. It is not unknown for Armoured Catfish to wear down or otherwise damage their barbels in harsh substrates and suffer from an inability to feed properly, and subsequently die. Water-worn gravels are to be preferred to sharp grained types for this reason. Although I would suggest sharp edged substrates have no virtues for aquarium use anyway.
Apart from the form of the downturned, barbel-adorned, strong, mouth, there are other features in the design of Armoured Catfish which indicates their evolution as bottom dwelling fish. They have flattened undersides which are generally light in colour, camouflage colouring being unnecessary for this unseen, bottom-hugging, area. The smooth armour plated upper body, by contrast, is mostly heavily patterned to break up the body form when seen against the substrate. The smoothness of the body permits the water to flow unimpeded over the browsing fish in the flowing waters they favour. The rigid spines of the pectoral fins assist in achieving stability in certain conditions, and the dorsal fin spine gives protection from would-be predators menacing them from above.
One of the most endearing features of Armoured Catfish are their “winking” eyes. The eyes are frequently turned about, almost chameleon-like, in an inquisitive looking-around exercise, as well as turning completely down from time to time giving that “winking” effect. Because “Corys” are diurnal this engaging feature is readily observed. Some fishkeepers are convinced this is a friendly gesture directed towards them by their boney friends in the fish tank. Alas, it is not as it seems. I fear such thoughts are pure fantasy. The eye lenses are simply being cleaned by this action.
The armour of the catfish body does much to protect the fish from parasitic infestation, but they are not immune from every malady. Wild caught fish are often troubled by bacterial infections affecting their soft abdominal region, manifesting as red patches, like sores. Treatments are often as hazardous as the problems they are intended to cure. Armoured Catfish react badly to many conventional “fish cures”. Generally it is probably best to restrict treatment to broad spectrum antibiotics and hope this will stem the progress of the problem sufficiently to allow the fish’s own immune system to cope eventually and facilitate a recovery. But, frankly, in my experience, advanced infection stands little chance of successful recovery from treatment! This factor should be born in mind when purchasing Armoured Catfish. Make good and sure that the stock in the dealer’s tanks has been held long enough to be seen to be sound and healthy before buying. The use of a “quarantine” tank of your own is something I cannot recommend too strongly – and I do not mean just for Armoured Catfish, but ALL new fish acquisitions. Keep any new fish purchases away from the intended aquarium for a period of not less than one week, and be as sure as you possibly can that nothing unseen and sinister is hosted by the new arrival. If a problem arises in your main aquarium with other fish you would be advised to take out the “corys” and keep them away from the treatments necessary, safe, and effective for the other fish, but potentially hazardous for the armoured catfish.. The quarantine tank has many potential uses.
There are, of course, dedicated enthusiasts who collect and revere their precious catfish, but quite apart from them there are few hobbyists without at least one or two corys in their possession. It is probably true to say that most of these initially find a place in the home aquarium because of the mistaken concept that they are a necessity, as utility workers in the “housekeeping” department. Well, that’s okay for starters, but once acquired the true fascination of the fish soon becomes apparent. If there is only one fish in your tropical aquarium which has been given the privilege of being pet-named it is most likely to be a catfish or a cichlid. On balance, I am confident that Armoured Catfish would collectively top the poll.