[Ebook] The New Guide to Aquarium Fish – Catfishes – Corydoras, Brochis and Aspidoras

Catfishes

Corydoras, Brochis and Aspidoras

These small, armoured catfishes are ideal inmates for the community tank, where they will swim in small groups in search of food. Corydoras, with over 100 different species from which to choose, are often the first cat-fishes to be kept. Dianema longibarbis (Porthole Catfish) and Dianema urostriata (Flagtailed Catfish) belong to the same family as the Corydoras, but grow to 14 cm (5 1/2 in). They are placid fishes, and again are well suited to life in a furnished aquarium. Very similar, though smaller than most Corydoras, are the Aspidoras with only a dozen or so species.

Brochis, on the other hand, with three species, are generally larger than Corydoras, about twice the size, but like the latter are peaceful. These catfishes are found throughout most regions of tropical South America, and are regularly imported for the aquarium. They have two rows of dermal bone plates on each side of the body, almost completely encasing the fish. Two pairs of short barbels are well suited to sifting the substrate for food; longer, more slender or more complex barbels would be quickly damaged or abraded. These barbels form a funnel into the mouth as the catfish eats, giving it a taste of what is about to be ingested, and allowing it to identify items to be discarded.

Corydoras and its relatives are often observed dashing to the water surface and back to the bottom of the aquarium. The reason is that this group is able to survive in poorly oxygenated waters by supplementing the dissolved oxygen extracted by the gills with atmospheric air. This is gulped in as the fishes break the surface and stored in the hind gut, which is highly vascularized. Here direct oxygen exchange into the bloodstream is undertaken. Corydoras surfacing in this way in the aquarium does not necessarily mean low levels of dissolved oxygen in the tank: it seems to be a reflex action irrespective of necessity. A good indication of the condition of any of this group is the presence of a body sheen, which is visible on all healthy specimens.

Brochis are larger than Corydoras, and distinguished by their longer-based dorsal fin: Corydoras have only 6 to 8 dorsal fin rays, whilst Brochis have from 10 to 17. The only species of the three to have been bred in small numbers is Brochis splendens (emerald catfish), the smallest member of this genus, and the one most often offered for sale.

All these species are best kept in small groups of four to eight specimens. They benefit from being one of the few catfishes active in the daytime, whereas many other groups are nocturnal. Ideal foods for these catfishes are small aquatic invertebrates such as Cyclops, Tubijex, and Daphnia, supplemented with commercial flake or pelleted foods. Such a diet is recommended for conditioning the fishes for breeding.

Breeding Corydoras

Sexing Corydoras is fairly easy. In adult specimens, the female has a fuller, more robust body compared to the more slender male. This is more apparent when viewed from above. Many, though not all, Corydoras show dimorphism in the ventral fin shape, with females exhibiting fan-like finnage, and males with spear-shaped ventral fins. The easiest species with which to start a breeding programme is Corydoras paleatus (Peppered Catfish). This species is also the variety most commonly found in a local aquarium dealer’s tanks.

In order to breed Corydoras, it is recommended that they be removed from the community tank into a small tank away from other species. Whilst Corydoras will spawn in the community tank, there is always the probability of the eggs being eaten by other inmates. The breeding tank need be no larger than 10 litres (2’/2 gallons) capacity, with a fine sandy base, and sparsely decorated with one or two broad-leaved plants. Filtration of some kind is essential. Introduce the Corydoras at a ratio of two males to each female. A trio is preferable to six specimens in this size of aquarium.

Often, if in breeding condition, they will require no inducement to spawn, but if they seem reluctant, gradually lower the water level of the tank by 30 to 40 per cent over five days. On the sixth day replace what has been removed with fresh water of a marginally lower temperature. This is to imitate the natural environmental conditions of Corydoras, who spawn at the onset of the rainy season. Often the males will excitedly follow the female around the tank as she looks for a suitable spawning site; this is a good indication that spawning is to commence shortly. One of the males will then position himself directly in front of the female in the classic T-formation. The two fishes will shudder while the female releases a small number of eggs which are clasped in her ventral fins (hence her expanded ventral finnage). The male simultaneously releases sperm to fertilize the eggs. The female then places the adhesive eggs onto a flat surface that has been cleaned prior to spawning. This may be on the plant leaves, or more often than not, on the side of the aquarium. Whatever the anchorage point is, it will be in the upper part of the water column, not on rocks or the substrate.

At this point it is recommended that either the adult fishes or eggs be removed. The eggs can be removed using a razor blade or something similar, taking great care to avoid damaging them, and placed in a plastic sieve of the type available from most aquarium shops. The sieve is then suspended just below the water surface. The water in the sieve is constantly replenished by means of an air-operated sponge filter, in order to ensure that the eggs are always in well-oxygenated water. They hatch within about 48 hours.

After absorbing their yolk sac the young fry can be transferred to a small, unoccupied aquarium, and fed newly hatched Atemia (brine shrimp), and as they grow, offered Daphma and crumbled flake foods.

Once you have mastered one of the commoner easy species such as Corydoras paleatus (the peppered Corydoras) you can move on to one of the more difficult species like Corydoras panda. This fish was named on account of its coloration: it looks a lot like a panda, with black eye patches on a light body.

To breed this lovely creature you will need to use a similar set-up to that used for the peppered Corydoras, but include a number of artificial mops on the bottom and hanging from the top. More often than not Corydoras panda will spawn into one of these, rather than out in the open. It is then an easy job to carefully pull the eggs off the mop and hatch them in the same way as before. This species is not so prolific with only 20 or so eggs produced each spawning, instead of up to 100 for the common species. It also tends to be seasonal in its spawning habits, so no matter how carefully the fishes are conditioned no spawning activity will take place until the correct time of the year – the onset of the rainy season.

Breeding Aspidoras

Aspidoras are generally smaller than Corydoras, and although similar, differ from the latter in minor anatomical characteristics of the skull that are not superficially apparent. Aquarium care is similar to that for Corydoras.

Breeding Aspidoras has proven a little more difficult than breeding the commoner species of Corydoras, but it is on a par with many of the wild-caught Corydoras. The aquarium should be set up with soft water and a mop suspended from a corner of the tank. This should be positioned so that its top is just beneath the water’s surface. Additional mops can be positioned on the bottom of the aquarium to provide cover for the adults. It is best not to use a substrate in the
breeding tank.

Sexing Aspidoras can be achieved in the same way as for Corydoras, but the differences in the finnage may be a little more difficult to identify. When selecting potential breeders choose a female which has a nice plump body and a male which is active and showing good coloration. In this case use only a single pair instead of the trio suggested for Corydoras. The breeding pair should be placed in the breeding aquarium and conditioned on plenty of live foods.

Aspidoras usually spawn during the early hours of the morning before sunrise, so you are most likely to find the eggs first thing in the morning. They are amber coloured and will most likely be laid in the mop just under the water’s surface. The adult pair can now be removed to another aquarium, together with the mops from the bottom of the breeding tank. While the eggs will hatch if left in the mop, they will be more prone to fungus because of the lack of water movement. It is far better to carefully remove the eggs from the mop and spread them out on the aquarium bottom. Using this method virtually 100 per cent of the eggs will hatch.

A good spawning will produce in excess of 100 eggs. These hatch on the fourth day and the fry will be free-swimming a day or two after that. The fry will eat newly hatched brine shrimp as a first food, followed by other live and commercial foods. If well fed the babies will reach 3 cm (1/4 in) long in only 10 weeks.

The newborn fry look rather like small tadpoles, because their finnage has not yet developed properly. The dorsal, adipose, anal, and caudal fins are joined together into one long fin, which surrounds the rear half of the body. As they grow this “super-fin” splits into four separate parts with the anal fin differentiating first, followed by the dorsal and then the tiny adipose fin.