Callichthyidae. Subfamily Corydoradinae
Upper Amazon basin in Ecuador, Colombia, Peru and Brazil.
Rivers and tributaries.
Maximum Standard Length
Aquarium SizeTop ↑
A tank measuring 18″ x 12″ x 12″ (45cm x 30cm x 30cm) – 42.5 litres is adequate for a small group of these.
An Amazon biotope setup would be very simple to arrange. Use a substrate of river sand and add a few driftwood branches (if you can’t find driftwood of the desired shape, common beech is safe to use if thoroughly dried and stripped of bark) and twisted roots. A few handfuls of dried leaves (again beech can be used, or oak leaves are also suitable) would complete the natural feel. Aquatic plants are not a feature of this species‘ natural waters. Allow the wood and leaves to stain the water the colour of weak tea, removing old leaves and replacing them every few weeks so they don’t rot and foul the water. Use fairly dim lighting if possible.
Alternatively, it also does well in a more standard, well-planted tank. A good maintenance regime is essential with this species as it’s sensitive to deteriorating water conditions. As with all corys, don’t use undergravel filtration and ensure the substrate is kept scrupulously clean. These cats are sensitive to poorly maintained or dirty substrates and can lose their barbels if kept in poor conditions.
Temperature: 72-77°F (22-25°C)
Behaviour and CompatibilityTop ↑
Very peaceful and suitable for many community tanks. Don’t keep it with anything very large or aggressive. Good tankmates include small characins, cyprinids, anabantoids, dwarf cichlids and other peaceful catfish. Always try to maintain Corydoras in groups as they’re far more confident and active in the presence of conspecifics. A group of at least six is best.
Like most cories, it can usually be sexed easily when viewed from above. Females are noticeably rounder and broader-bodied than males, especially when full of eggs. In this species females also tend to grow larger than males, and have much less patterning on the body. Males of certain populations develop an enlarged dorsal fin.
Set up the breeding tank (18″ x 12″ x 12″ or similar is a good size), with either a bare bottom, sand or fine gravel substrate. Use air-powered sponge or box-type filtration as fry won’t be sucked into these and provide some clumps of vegetation such as java moss. A temperature of around 75°F and a pH of 6.5 should be fine. Filtering the water through peat is useful, as is the use of RO water.
It’s always better to have a higher ratio of males to females when breeding corys and 2 males per female is recommended. Condition the group on a varied diet of live, frozen and dried foods. When the females are visibly full of eggs perform a large (50-70%) water change with cooler water, and increase oxygenation and flow in the tank. Repeat this daily until the fish spawn.
It’s worth observing a couple of notes on general cory breeding at this point. Many species are seasonal spawners, breeding during the wet season in their native countries. This occurs at the same time of year as the UK winter, so if summer breeding attempts are failing, it may be worth waiting until winter before trying again. Additionally, it can take several years for certain species to become sexually mature, so be patient. Finally, different tactics may sometimes be required, such as timing of water changes, oxygenation levels etc. It’s also been suggested that the addition of water from a tank containing spawning or just spawned corys (this can be the same or a different species) may induce spawning behaviour in some of the more “difficult” species. It’s likely that this can be attributed to hormones released by the spawning fish acting as a chemical trigger. Basically, if you aren’t having any luck, don’t be afraid of trying different approaches.
If the fish decide to spawn, they will usually lay their eggs on the tank glass, often in an area where water flow is quite high. Spawning behaviour is characterised by an initial increase in activity and excitement, before females begin to actively pursue males and vice versa. Unlike most other corys, the spawning participants don’t take up the classic “t-position”. Instead eggs are laid directly onto the aquarium glass or other suitable surface before being fertilised by the male. If being maintained in a group they may spawn in this way en masse.
The adults will sometimes eat the eggs, so once spawning is complete you have a couple of choices. Either remove the adults and raise the brood in the same tank, or move the eggs and raise the fry elsewhere. If you decide to move the eggs, you’ll find they’re quite robust, and can usually be gently rolled up the glass with a finger. The new container should contain the same water as the spawning tank and be similarly well-oxygenated. Wherever you decide to hatch the eggs, it’s always best to add a few drops of methylene blue to the water to prevent fungussing. Even then, some eggs will probably fungus, and these should be removed as soon as they’re spotted in order to prevent the fungus spreading. Other options include adding an alder cone to the hatching container (these release various beneficial chemicals). Some hobbyists even use certain species of freshwater shrimp to pick any fungal spores from healthy eggs. Cherry shrimp, Neocardina heteropoda work well. These will eat diseased eggs, but leave healthy ones unharmed.
The eggs are smaller than those of most other corys. They hatch in 3-5 days and once the fry have used up their yolk sacs, they’ll accept microworm and brine shrimp nauplii as first foods. They seem to be less susceptible to disease when kept over a thin layer of sand, rather than in a bare-bottomed setup.
There are currently over 180 described species of Corydoras (commonly shortened to “cory”), making it one of the most speciose of all South American fish genera. There are also loads of undescribed species, many of which have been assigned a “C number” for identification purposes. This is a very simple system of numbering and is similar to the L number scheme used to identify undescribed Loricariids. Both systems were implemented by the German aquarium magazine DATZ (Die Aquarien und Terrarienzeitschrift), but have proved to be invaluable tools and are now used widely by aquarists worldwide. It’s partly this tremendous diversity (along with their undeniably cute looks) that puts corys among the most popular fish in the hobby.
They’re also very peaceful aquarium residents. Although they’ll consume bite-sized items such as eggs or fry, aggression towards other species is virtually unheard of. Intraspecific hostility is similarly unusual, occurring in only a handful of species (mainly being confined to the “long-nosed” varieties). Provided space isn’t an issue this rarely results in physical damage, though. In nature most species occur in large schools and as such do best when kept in a group in captivity.
Most corys are primarily benthic (bottom dwelling), although a handful of exceptions do spend the majority of their time in open water. Unfortunately this behaviour often means that they’re purchased and sold as scavengers that will “clean the bottom” of your community tank. While they’ll certainly polish off any uneaten morsels that reach the substrate, they won’t keep the substrate “clean” as such. In fact maintenance of the substrate becomes more of a primary concern if your tank contains a few corys, as they can develop nasty infections of the barbels if kept in dirty or otherwise unfavourable conditions. It should also be said that they won’t do well if expected to survive on the scraps of food that escape the fish above. Always use sinking varieties to ensure your corys receive the right amount of food.
All corys are facultative air breathers, meaning they have the ability to breathe atmospheric air to a certain extent if necessary. They possess a modified, highly vascularised intestine to aid in the uptake of atmospheric oxygen. This adaptation allows them to survive if their habitat becomes oxygen-deprived for any reason. In the aquarium you’ll see them darting to the surface to take in gulps of air on occasion. This is perfectly natural and no cause for concern unless water conditions are deteriorating, in which case the frequency of visits to the surface will usually rise correspondingly.
Corys are part of the “armoured” catfish group, and instead of scales possess two rows of bony plates running along the flanks. The genus name is composed of the Greek words cory, meaning helmet and doras, meaning skin (here used incorrectly to denote “armour”). They also have very sharp pectoral fin spines, which are easily caught in the mesh of aquarium nets and can also produce a painful “sting” if they penetrate the skin. Care should therefore be exercised when handling or moving corys for any reason.
Unlike most of its congeners C. elegans has an interesting habit of spending a good deal of its time swimming in open water, where you’ll see it hovering in groups or resting on the leaves of plants. It can be tricky to identify correctly as it’s comparable in appearance to numerous other species, most notably C. undulatus, C. nanus and C. napoensis. C. undulatus differs primarily in terms of body shape, being noticeably less elongate than C. elegans. C. napoensis is best distinguished by looking at the dorsal fin of the male. This has a distinct solid black upper portion, unlike the rather more random markings in the dorsal of C. elegans males. C. nanus is the most slender of the group and males have less patterning in the dorsal than the others. To make matters more confusing C. elegans itself is very variable in colour and patterning depending on locality. Some of these differ enough to have been considered worthy of their own C number. Some experts refer to this whole group along with other similar species as the “C. elegans group” and believe they may eventually be reclassified to their own genus.