Corydoras is a genus of freshwater catfish, the name being derived from the Greek words, “Kory”, meaning helmet and “doras”, meaning skin. There are probably more than 160 distinct species of Corydoras from which the aquarist may choose and this includes a large number of visually stunning fishes that are bound to enhance any home aquarium.
Is the Black-back Corydoras a good community fish? Black-back Corydoras should be considered to be an excellent community fish assuming that the community is one of non-aggressive, non-predatory species. Black-back Corydoras is suitable for all community aquariums.
Key Facts about Black-back Corydoras
|Common name(s)||Black-back Corydoras|
|Scientific name||Corydoras duplicareus|
|Originate from||Upper Negro River basin, in South America|
|Care required||Easy to care for and hugely popular|
|Temperament||Placid and timid shoaling fish|
|Colour & Form||Flat-bellied body with its back arched ahead of the dorsal fin|
|Lifespan||Up to 15 years|
|Adult size||2.5 inches|
|Diet||Omnivorous – eat Bloodworm, Tubifex worms and sinking pellet food in the aquarium.|
|Aquarium size||24 inches in length or greater|
|Compatible with||Most other Tetras, Barbs, Danios, Guppies and other livebearers, dwarf cichlids, smaller Gouramis, catfish and loaches that live in fairly neutral, soft water|
|Avoid keeping with||Large and/or aggressive species in too small an aquarium|
|Breeding||Easy if you put the fish in the right environment.|
|Water temp||68 – 75 Fahrenheit|
|Water pH||6.4 to 7.4|
|Water hardness (dGH or dH)||2 to 10 dGH|
Origins of the Black-back Corydoras
Corydoras species are distributed in South America, east of the Andes to the Atlantic coast and from Trinidad to the Río de la Plata drainage in northern Argentina.
Corydoras range from around 1 inch in length to 5 inches in length. Corydoras are protected from predators by their body armor and by their sharp, usually venomous spines.
Characteristics of the Black-back Corydoras
Black-back Corydoras is found in the Upper Negro River basin, in South America.
Black-back Corydoras is a striking and most distinctive fish. It is usually found in nature is slow-flowing streams, on the margins of larger rivers, in marshland, in ponds and also in lakes but seldom, if ever, in stagnant water.
The Corydoras has a flat-bellied body with its back arched ahead of the dorsal fin. Corydoras are generally bottom-feeder, which is not to suggest that they eat rubbish, rather they thrive on food which has settled to the bottom. In the aquarium, Corydoras are regularly seen taking algae off the glass of the tank or off rocks within the tank.
Contrary to popular belief, Corydoras prefer to live in small shoals (in nature, such shoals can comprise hundreds, even thousands, of individuals) and, unlike catfish, are active during the daytime and early evening rather than during the night.
It may surprise you to learn that Corydoras can live to an age greater than twenty-years so be sure that you know about the species that you are buying because it may be a long-term relationship that you will enjoy.
Corydoras are intolerant of salt and even a small amount can be harmful to them (though aquarium salt, properly administered may be used to cure Corydoras of white spot – “ich”, “ick” or, to give it its posh name, “Ichthyophthirius multifiliis”.
If threatened, Corydoras is likely to rest on the substrate of the aquarium, protected by its armored skin and its (ofter) venomous spines so it is generally left alone by other species.
The Corydoras, in addition to its body armor (as opposed to the more conventional scales amongst other species of fish), had four spiked and usually poisonous barbs – one under each eye, one on the adipose fin and one on the dorsal fin. In most cases, the leading edge of the dorsal fin is colored and this may be as a warning to potential predators that it is “weaponized”.
Black-back Corydoras will grow up to around 2.5 inches in the aquarium and live for up to 15 years but note that Corydoras can be long-lived, reaching ages of in excess of twenty years so don’t be surprised if your Corydoras outlives “expert” predictions.
Black-back Corydoras prefers fairly soft, neutral water with a pH of 6.4 to 7.4 with a temperature range between 68 and 75 degrees Fahrenheit and up to 10 dGH.
Black-back Corydoras enjoys soft to medium, slightly acidic or neutral water conditions so it will be comfortable with other species of similar size that prefer this type of water chemistry.
The female is generally larger, deeper and wider bodied than the male and displays less intense color than the male in the body at spawning times. The male tends to be somewhat slimmer and its coloring is more intense in the body than the female.
The Corydoras, being that it is a river and lake dweller, enjoys flowing water not still or stagnant water so the aquarium needs to be set up in such a way that it has a current of water from one end to the other. This is generally provided by routine aerations and filtration systems. In its natural habitat Corydoras enjoys water flow, The Corydoras is adapted to that environment.
Remember that Corydoras are not intended to clean the tank bottom. If keeping Corydoras, remember to include sinking food that, when presented, will sink to the bottom of the tank, especially for your Corydoras
The Black-back Corydoras has a silver-colored body below the spine. Running horizontally along its spine from behind the gill plates to the rear of the caudal peduncle is a golden band. This rich, golden color extends into the gill plates themselves. Above this band to the top of the dorsal area, the Black-back Corydoras is black and this bleeds slightly into the caudal fin. The leading edge and the rays of its dorsal and adipose fins are also black – but this is less evident in the female, which has softer, rays. In front of the dorsal fin, on top of its back and extending down to the top of the gill plates is an iridescent golden patch of color. In front of that is a vertical band of black which covers the eyes and extends down as far as the underside, where it ends. The remaining fins are generally clear (hyaline). The coloring appears to be deeper in the males, particularly in the leading edge of the dorsal fin.
The Black-back Corydoras is characterized by having a slightly extended, grey snout and relatively long barbels which will be exposed to possible damage on sharp or abrasive surfaces, making them susceptible to infection. It appears to be a particularly inquisitive little fish and it is quite captivating to watch it blinking back at you through the glass of the aquarium.
Note that the barbels are delicate so the substrate of the tank should be fine sand, rather than pebbles, the latter of which could cause damage, leading to infection.
Black-back Corydoras really enjoys being in the shade so a well-planted tank is beneficial to it.
The Corydoras is a gentle, timid fish but it is also great fun to sit and watch. It is not known to be aggressive and will get on well with pretty well any tankmates, so it is just fine putting it with other community species unless such species are known to be aggressive and/or predatory. Remember that the Corydoras carries a venom that can harm tankmates, including themselves if released in quantity. This is highly unlikely; I have never witnessed it but it is theoretically possible.
The Corydoras is a shoaling fish and should be kept as a group of at least six fish of each species that you choose to keep. There is every reason to have a decent-sized shoal in a decent-sized aquarium to ensure that you Corydoras has plenty of space in which to behave naturally.
Having plenty of vegetation to break up lines of sight will also help to protect your Corydoras from predation and overly-bright lighting is recommended but it is obviously advised that Corydoras are not kept with predatory species, as they are a very peaceful fish and may be seen as prey.
Having a clear, broad area of a fine substrate will enable your Corydoras to forage naturally at the bottom of the aquarium.
Most Corydoras will, periodically, dart up to the surface to take a gulp of air, returning promptly to the bottom once more. This is quite natural so don’t be alarmed when you first see it.
Overall, the Black-back Corydoras is a most attractive and most elegant addition to your aquarium.
Sexual differences in Black-back Corydoras
It is fairly easy to distinguish the sex of adult Black-back Corydoras because the adult female is often larger and broader whilst the male tends towards being slimmer and with more distinct coloring. The female is also fuller-bodied when viewed from above, especially when carrying eggs (gravid).
The Corydoras usually inhabits the bottom of the aquarium. It tends to feed in the lower areas of its environment, as it is adapted for rooting out food from the substrate and will often bury its mouth into it. They love blood worms, tubifex worms and mosquito larvae at least a couple of times each week but will accept freeze-dried food as well as pellet food designed to sink quickly to the bottom.
The Corydoras is, by nature, a shoaling fish and it is generally recommended to purchase at least six fish but preferably twelve to twenty-four fish, as their nature is to swim together like a shoal, against the flow of water and they will tend to thrive much better as a shoal. Corydoras are excellent community fish and are ideal for intermediate aquarists assuming that the soft, neutral and flowing water and appropriate breeding conditions required are provided and maintained.
It is generally advised that the minimum tank size for Corydoras should be one of at least 24 inches in length or more due to the fact that a shoal of around six per species is maintained. This will enable your small shoal to move around freely. A smaller tank might be too restrictive and the fish will suffer as a result whilst a larger tank is always to be recommended.
Assuming an average adult size of three inches and an average shoal of six Corydoras of each species then I would, in addition to recommending a tank length of twenty-four inches, assuming one species I would further recommend adding an additional twelve inches for each additional six Corydoras (of the same or different species and of similar size.
There is a predominance of so-called “Nano tanks” available but, being old-fashioned, I prefer my fishes live in an environment which, at least, attempts to mimic nature, rather than living in what I would liken to a prison cell. The tank should be well-planted but with clear areas where the fish can swim freely. The water should have a decent amount of movement, as Danios enjoy swimming against a flow of water.
Corydoras are easy to sex when they are mature, where the female has a slightly fuller body when she is carrying eggs (gravid) than the male.
The general rule for Corydoras is that by keeping six or more of the same species in your aquarium they will be fully aware of which is male and which is female, even if you don’t and they will act accordingly when the time comes for breeding.
Black-back Corydoras – Videos
How do Black-back Corydoras breed?
Corydoras, in general, breed somewhat differently from other types of fish. It is generally true that the female will attach her mouth to the genital organ of the male and will then drink the sperm. The sperm then moves swiftly through the digestive system (without being digested) and will then be expelled, together with her eggs through a pouch formed by the pelvic fins.
After ingesting the sperm, the female will then move away from the male and will later lay her eggs in a place of her choosing.
This is true of Black-back Corydoras, however, the female will generally hold up to 2 to 4 fertilized eggs between her pelvic fins then deposit these eggs in one of the areas that she has been previously preparing. The process will continue until the female is depleted of her eggs. Typically, a female Black-back Corydoras will lay up to 100 eggs, which can take two to three days to complete.
Corydoras place their eggs rather than scatter them. In respect of preparing a breeding tank for the Corydoras, it is generally recommended that the bottom is covered in small, rounded pebbles or fine substrate, avoiding sharp-edged objects that can damage the sensitive barbels.
As the female Corydoras becomes ripe with eggs, the difference between the sexes will become more evident, as the body expands because it is carrying eggs. If you plan to attempt to breed Corydoras then it is recommended that you have a breeding tank prepared. Such a tank can be empty but a soft substrate is recommended, as your Corydoras will prefer to feed by foraging in the substrate for food and the female will lay her eggs there.
The water should have moderate aeration, bearing in mind that Corydoras do not enjoy still water.
As the female comes close to spawning, she will start cleaning the surface of leaves or the aquarium glass on which she will lay her adhesive eggs.
In total, the female Black-back Corydoras will lay around up to 100 eggs during a single spawning.
Thereafter, the adults will take no further part in rearing their offspring and may eat the eggs, given the chance so it’s best to return them to the breeding tank.
It takes around one to two to three days for the eggs to hatch, depending on the water conditions and temperature and around a further two to three days or so for the yolk sacs to be depleted and the fry to become free-swimming.
In a well-planted aquarium, the Corydoras will often spawn in the community tank and at least some of the fittest fry will survive to adulthood.
In a breeding tank, it is always a good idea to include a few aquatic shrimp, as they will consume any unfertilized or dead eggs but won’t tend to predate on viable eggs.
Breeding tank for Black-back Corydoras
You should prepare a tank of around ten gallons in size with mature, soft, acidic, flowing water. The water should have a low level of light and broad-leaved plants on which the female will lay her eggs (as well as on the aquarium glass. It is recommended that the substrate consists of a fine substrate (sand) without sharp edges.
Arrange your tank heating so that you can slowly remove up to half of the tank water and then replace it with collected rainwater and repeat this daily until the Corydoras spawn. This water and temperature change will encourage spawning, as it mimics nature. The rainwater is most important.
Corydoras prefer to spawn where the water is flowing so a decent pump is required to synthesize that flow.
Feed up your Corydoras on bloodworm, which will sink to the bottom and burrow into the substrate. Your Corydoras will love rooting out the bloodworm and it can help to trigger spawning.
You may also wish to introduce baby brine shrimp, mosquito larvae or tubifex worms as an inducement to reproduction and live food will be very much appreciated.
Reduce the water movement by turning down the pump – only regular aeration is now required. Keep the lights off (or very low) and the tank dark (of fairly dark) because eggs and fry can be particularly sensitive to the light.
The eggs will hatch typically in one to two days depending on tank temperature and conditions and the fry will become free-swimming after around three days after hatching. Keep the tank more-or-less unlit for the first week or so then gradually increase the lighting. Bear in mind that the eggs and fry of a fish as small as the Corydoras will be tiny indeed so you may need to use a magnifier “app” on your smartphone or a macro lens to see anything at all. A collection of eggs is generally easy to spot, as they look like a collection of tiny, tiny pearls.
The newly hatched fry will feed firstly on their yolk sac but, once free-swimming, can be fed infusoria (particularly rotifers) and will also thrive on egg yolk during the first two to four weeks.
Once the fry are free-swimming and their yolk sacs are depleted, then add baby brine shrimp and/or white worms. Once the fry are sufficient in size not to be treated as a snack then they can be introduced into the community tank where they will join the existing shoal. Before moving the adolescent fish into the community tank ensure that you have balanced the water temperatures to mitigate the risk of White Spot or other diseases being triggered.
Unless you are breeding commercially, you may wish to consider moving the fry into the community tank sooner rather than later. It may seem harsh but the adult fish in the tank will deal with any fry that are unlikely to survive to adulthood in the wild and you are synthesizing, to the best of your ability, a wild environment. The fittest fry will probably survive whilst the rest will be dealt with by the community.
Should your Black-back Corydoras have a special diet for breeding?
Adult Corydoras don’t need any particular inducement to breed. That said, it has been suggested that adding tubifex, bloodworm, or mosquito larva may encourage them, presumably because the addition of a new food may “fool” the fish into thinking that it is breeding time. From my own experience, I would always recommend keeping all of your fish in the best possible condition at all times, as this is good for the wellbeing of your fish.