Seasonal imports from South America

Seasonal imports from South America

Late autumn is when many of the more unusual South American fishes turn up in aquarium shops. Collectors and exporters can more easily obtain many South American species during the rainy season, when the fishes move out of the deep rivers and lakes they have spent the dry season in, and out towards the shallower streams and pools that they feed and breed in. Aquarists reap the benefits by getting to see many unusual and interesting species that are not seen at other times of the year.

Broadly speaking, South American fish come from two types of habitat, whitewater rivers and blackwater rivers. Whitewater rivers, are fast-flowing and turbulent, and collect a great deal of silt from the surrounding land. This makes them cloudy, and hence the name. Blackwaters, by contrast, flow slowly and collect little silt along the way. Instead, organic compounds leach into the water from decaying leaves and wood, staining the water dark brown. So while blackwater is very clear, it is also very dark. The two types of water also differ greatly in water chemistry. Whitewater rivers, such as the Amazon, have an approximately neutral pH and low to moderate hardness. By contrast, blackwater rivers, like the Rio Negro, have a very low pH (typically around pH 5) and virtually no hardness at all.

Because blackwater rivers are mineral poor, things like snails and crustaceans are very scarce. In fact, blackwaters contain comparatively little life because of the overall lack of nutrients, and many of the animals in blackwater rivers depend upon the land for food, either directly or indirectly. Many of the smaller fishes eat insects and spiders that fall onto the water, while larger fish take fruits that fall from the trees. The arowanas will even jump out of the water to take small animals perched on overhanging tree branches, and have consequently become known as "water monkeys"!

For the aquarist, the key thing is that whitewater species generally adapt well to neutral or alkaline system and tolerate a wide range of water hardness values. Blackwater species, by contrast, need soft and acidic water to do well, particularly if you want to breed them. The acidity of blackwater rivers seems to inhibit the life cycles of many bacteria and parasites, and the fishes from these environments are consequently much less able to deal with infections than other species. It is therefore important to keep these species in tanks that are scrupulously clean and where water changes are frequent and filtration generous. In short, they need much the same care as wild-caught discus, which are classic blackwater fish.


One the more unusual South American cichlids is an infrequently seen species of wild angelfish, Pterophyllum leopoldi. Known as the long-nosed or spotted angelfish, older aquarium books frequently refer to this species bu a now-obsolete name, Pterophyllum dumerilii. Although similar to wild common angelfish in terms of colour, it has a rather long snout and a distictive black spot at the base of the dorsal fin. Kept in appropriate water conditions this is a superb aquarium fish, but in common with other blackwater species, it prefers soft and acidic water and is extremely sensitive to poorly-filtered water. In particular, it does not tolerate high levels of nitrate, i.e., anything above 20 mg/l, so frequent water changes are absolutely essential. Pterophyllum leopoldi is a schooling fish when young but territorial when mature. Since angelfish are virtually impossible to sex reliably, it is best to buy a group and then allow a pair to form naturally. This species has been bred in captivity in a similar to way to common angels. One peculiarity of this species compared with the common angel is that it eats a significant amount of green food. Soft-leaved plants will be pecked apart, but spinach, blached lettuce, and algae-based flake food can all be used as a more convenient and inexpensive alternative.

Another excellent medium-sized (around 10 cm) cichlid is Biotodoma cupido, sometimes known as the cupid cichlid. They are nicely coloured fish, with a pinkish-green body marked with a dark band across the head and a dark spot below the dorsal fin. Fin colour depends somewhat on where the fish were collected, with the dorsal, anal, and tail fins being green, blue, or red. Although territorial and somewhat aggressive, it works well with things like characins and armoured catfish. The cupid cichlid is found in both whitewater and blackwater habitats and is pretty adaptable as far as water chemistry goes. On the other hand, it is very sensitive to poorly filtered water and high nitrate levels, which has given it a reputation for being a bit delicate. Kept properly, this fish is colourful and interesting to watch, being one of the "earth-eating" cichlids that constantly dig and sift the substrate in search of food. In the wild, they take insect larvae and small worms, but aquarium prove to be accommodating and take most frozen foods as well as suitable flakes and pellets.

The threadfin acara Acarichthys heckelii is a large (up to 20 cm) but peaceful species that may be territorial when spawning but otherwise tends to ignore its tankmates. Another widely distributed species, this fish is found in both whitewater and blackwater rivers, and generally adapts well to even quite hard and alkaline water conditions. It is basically pinkish-green in overall colour but with large golden yellow regions across the head and fins. Bright shiny spots arranged in rows cover the flanks and fins, making these fish especially eye-catching. There is a prominent eyespot about halfway along the flanks. A confirmed digger, this fish is best kept in tanks without rooted plants and makes an excellent choice for aquaria containing characins and catfish of comparable size.


While most people assume that all characins are more or less tetra-like, the characin group actually contains a whole range of types, including some big, powerful, predators. Thw wolf-fish Erythrinus erythrinus is a good example of this type of characin, and fish that is more comparable to a snakehead than a tetra. This is a surprisingly attractive fish that generally works well in community tanks with peaceful tankmates of comparable size, such as silver dollars, plecs, barbs, and non-aggressive cichlids. On the other hand, they are aggressive towards their own kind and likely any other fish that look similar. Wild specimens reputedly reach 25 cm in length and are able to survive in swamps, but in captivity they are usually smaller and despite the fact their are air-breathers, seem to need a mature tank with good water quality. Water chemistry is relatively unimportant. Erythrinus erythrinus is quite variable in colouration, with specimens from different places having different amounts of green, yellow, and red on their bodies. Feeding presents few problems, as these fish primarily eat large invertebrates in the wild, rather than fish, and so can be easily weaned onto earthworms, river shrimps, mealworms, and so on. Frozen foods, particularly prawns, silversides, and krill, are accepted as well. All in all, a lovely fish for the advanced aquarist looking for something colourful and unusual, but not too large.

Also known as the wolf-fish, Hoplerythrinus unitaeniatus is a bigger species that gets to about 40 cm in length in the wild, though usually a little less in captivity. Although quite hardy, this fish is a known jumper and has sometimes been found dried up on the floor adjacent the aquarium. It therefore needs to be kept in a tank with a sturdy cover. As with its smaller relatives, this fish is a predator and territorial towards its own kind. While some aquarists have had luck combining it with peaceful and robust fish of similar size, others have watched their wolf-fish become distinctly bad-tempered and bully even substantially larger species. Best kept alone.

One characin best avoided is by all but the most expert aquarists is the payara, Hydrolycus scomberoides. This predatory monster is a whitewater fish that feeds primarily on smaller fishes. Nicknamed the sabre-tooth tetra on account of the huge and protruding fangs borne by the lower jaw, it grows to over 1 metre in length in the wild, but for reasons unknown seems to be short-lived in aquaria. While seemingly hardy and adaptable, quickly taking to dead foods such as frozen silversides, most specimens seem to last only a few months before dying. A big tank with generous filtration is a must, and as with any predatory fish, be prepared to carry out large water changes at least once or twice a week.


South American catfish have been exceptionally popular with aquarists for decades. Topping the list are the Callichthyidae or armoured catfish, of which the genus Corydoras must easily rate as the world's most popular aquarium catfish. New species appear in the trade all the time, of which CorydorasÊvirginiae is a typical example. These beautiful little catfish is pearly pink in colour with a thick black band over the head and eyes, and second band across the back just behind the pectoral fins. All Corydoras need much the same thing: to be kept in a group of at least three specimens, to be provided with their own food rather than be left to scavenge, and to be kept away from aggressive tankmates such as territorial dwarf cichlids and nippy pufferfish. Though water quality needs to be good, on the whole Corydoras are fairly tolerant about water chemistry, and though they like soft and acidic water, adapt well to harder, more alkaline conditions if adjusted gradually. Corydoras prefer a soft substrate of sand, into which they will happily dig head-first, spewing out sand behind them in a comical and very entertaining way.

A closely related genus is Brochis, a group of small catfish that are superficially very similar to Corydoras but are more robust in shape and have a longer dorsal fin. Brochis multiradiatus is one of the more frequently encountered species and is known as the hog-nosed catfish on account of its distinctive snout. Essentially bronze-green in colour, these are very handsome catfish that do well in community tanks but appreciate a bit more space and water depth than do Corydoras. While still quite hardy, they are a little less forgiving that the commercially-bred common species of Corydoras such as peppered cories, and need a mature aquarium with good water quality. They are also perhaps a little less forgiving about water chemistry as well, and do best under neutral to slightly acidic and not too hard water conditions. Because this fish gets quite big (up to 10 cm) and needs to be kept in a group, these fish usually uproot most aquarium plants. Instead, keep in a tank with plants that are attached to wood (such as Java fern) or else float at the surface of the tank.

Even smaller than the Corydoras catfish are some of the driftwood catfish, such as the leopard woodcat Centromochlus reticulatus, often referred to by aquarists under an obsolete name, Tatia reticulata. This species gets to less than 3 cm in length and makes a delightful addition to the community aquarium. Juveniles are somewhat drab, pinkish-brown fish with vague mottling on the dorsal surface, but adults are spectacular little fish, with beautiful chocolate brown patches set against a pale pink ground colour. Maintenance is fairly simple as these fish seem to be quite adaptable as far as water chemistry goes. The only real problem is feeding them, as they are very nocturnal. Frozen bloodworms and other such foods will be relished, but take care that other nigh-feeding species, such as loaches, are not in the tank as well, or these little driftwood catfish are liable to miss out.

Pseudohemiodon apithanos is one of the most impressive of the Loricariidae kept by aquarists. Sometimes called the chameleon whiptail, this 30 cm catfish is typically light grey-brown with a dark band running dorsally from nose to tail, but if disturbed will turn completely black. A whitewater species, this catfish does best in tanks with neutral, fairly soft to moderately hard water. Unlike most other loricariids, this fish isn't particularly interested in caves or bogwood, and seems to be adapted to sandy areas, where it hides under leaf-litter. Presumably, it's colour changing abilities help it to blend in with its surroundings. In the aquarium, provide this fish with a large expanse of sand for it to dig into, and provide it with a mix of algae tablets and frozen invertebrates such as bloodworms. If you want to create some leaf-litter in your aquarium, oak leaves seem to work best. This species is completely peaceful, even towards its own kind.

One catfish often looked for but rarely seen is the handsome pimelodid, Pimelodus ornatus. An active catfish that gets to around 30-40 cm in aquaria, this species works very well in community tanks with fish of comparable size. Though it will eat smaller fishes it is otherwise easy to care food and will take pretty much any suitable food, from catfish pellets through to frozen bloodworms and live river shrimp. Found in both blackwater and whitewater rivers, it has proven to be adaptable and hardy, and thanks to its beautiful markings, an excellent specimen fish more easily managed than the larger predatory pimelodids. It is sociable though pairs sometimes squabble, so should either be kept singly or in groups of three or more.


Besides catfish, characins, and cichlids, South America also provides a nice selection of oddball species. One of the most popular is Colomesus asellus, the South America pufferfish. This non-territorial, schooling species is best kept in groups and being relatively small (around 8 cm when mature) makes a good choice for the home aquarium. A tank given over entirely to this species is a fun project, as these fish are constantly active and intensely curious. Single specimens tend to be a bit nervous, so try to get at least two or three specimens. They are open water fish that are found in both blackwater and whitewater rivers and adapt well to both soft and hard water conditions, and in fact are among the easiest pufferfish to keep. The only real problem with this species are its exceptionally fast-growing teeth, which typically need trimming once or twice a year. Cuticle clippers do the job nicely, and 1-2 drops of clove oil in a litre of aquarium water will make a bath within which the fish can be safely sedated. If you want to avoid such surgery, provide your pufferfish with lots of crunchy foods, particularly snails. Like other pufferfish, this species is sometimes a little nippy, and the fins of slow moving fish, such as Corydoras and livebearers do tend to be nipped. Faster fish, such as tetras, seem to work much better.

South America is also home to a variety of knifefishes similar, though only distantly related, to those found in Asia and Africa. Sternarchella schotti is one such species and a large (40 cm) but attractive subject for the advanced aquarist. A whitewater species it normally inhabits deep channels in major river systems where it uses its electric organ to navigate and probably to communicate with one another. In aquaria, these fish are territorial among their own kind, though peaceful tankmates such as catfish and large characins are largely ignored. As with other knifefish, this species is predatory, and besides worms, insect larvae, and other small invertebrates, it will also eat very small fish. Basic care is otherwise similar to the more widely kept black ghost knifefish, Apteronotus albifrons.

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