Osteoglossiformes

Also known as Peter's elephantnose, this fascinating species is currently the most common Mormyrid in the hobby. Sadly, its popularity means it is often kept in unsuitable conditions. To deny the fish a soft substrate really is cruel, as it uses its "trunk" to locate food hidden in the substrate. It also needs dim lighting, and will commonly become withdrawn and pine away if kept under bright lights. If you cannot provide suitable lighting, add food to the tank at lights out to al...

Originally classified in the genus Notopterus and reclassified in 1984, this is now the only described species of Xenomystus and has several interesting characteristics. Its swim bladder is specially adapted to act as an accessory breathing organ in a similar fashion to Polypteriids. It must rise to the surface to take a gulp of air periodically, often emitting a bell-like sound as it does so. X. nigri is often confused with the similar looking but far more aggressive Asian knifefish, Notopt...

This species is also referred to as 'Asian knifefish' or 'ghost knifefish' in the aquarium trade in the aquarium trade but arguably has no place in the ornamental hobby given its adult size and specialised requirements. It is sometimes confused with the African species Xenomystus nigri but is easily told apart by its larger adult size and presence (vs. absence) of a dorsal fin.

C. tamandua is quite a rare fish in the hobby, but is imported occasionally. It's not a good beginner's fish as it requires pristine soft, acidic water conditions, will generally not feed on standard foods and attains a very respectable adult size. It's also sensitive to many aquarium medications. It can sometimes be found as a contaminant among imports of the much more common Elephant Fish, Gnathonemus petersii. Unlike this species, C. tamandua has both upper and lower jaws exten...

G. niloticus is the only species in its genus and is utterly unique. Unlike other knifefish it has an extended dorsal rather thangiving rise to the alternative common name of upside-down knifefish. Despite this common name, it is actually more closely related to the Mormyrid group of species. It is a truly beautiful sight in motion despite its lack of bright colours, as it can move in virtually any direction with ease using its undulatingto 'steer'. It also produces a weak electrical d...

The common name of this surface-dwelling species is derived from it's appearance when viewed from above, the large pectoral fins giving it the appearance of a butterfly. In reality, these fins serve a dual purpose. They help to camouflage the fish, making it look like a dead leaf floating on the surface, and along with the caudal fin, power the incredible jumps that it is capable of making. The fish jumps from the water to catch flying insects or to escape potential predators and it can mak...

Like other members of the family Notopteridae this species differs from Gymnotiform knifefish in that its anal and caudal fins are fused together into one long, undulating fin running along the underside of the fish. There is only one other species in the genus. P. congoensis is a smaller, plain brown coloured fish found only in the Democratic Republic of Congo and is very rare in the hobby. P. afer is also infrequently imported and is one of the rarer knifefish species in the hobby. It can dev...

Although S. jardinii superficially resembles its Asian cousins, it is not considered as desirable an aquarium inhabitant, nor is it classed as being at risk in nature. It can be easily distinguished from the asian species by its much smaller scale size, greater lateral scale count (32-35 as opposed to 21-25 in the asian aros) and duller patterning. It differs from its Australian relative S. leichardtii by its more sloping head, downward-pointing barbels and patterned gill covers. The base colour...

This species is also referred to as 'royal knifefish' in the aquarium trade but arguably has no place in the ornamental hobby given its adult size and specialised requirements. It can be distinguished from congeners by presence of many small, dark spots on the anterior portion of the body which merge to form oblique, irregular stripes extending onto the anal and caudal fins posteriorly.

This species' name has been widely misapplied in the aquarium trade and hobbyist literature, most often in reference to the Southeast Asian species C. ornata, but unlike its relative is in fact very rarely exported for ornamental purposes although its is fished and cultured for food in India. It can be told apart from C. ornata by possessing fe...

This species is not collected for the aquarium trade at time of writing. In contrast to other members of the genus older juvenile and adult individuals lack dark markings on the body while the jaw is more pronounced.

This species is also referred to as 'clown knifefish' in the aquarium trade. It arguably has no place in the ornamental hobby given its adult size and specialised requirements but remains inexplicably popular and an albino form has even been line-bred for the purpose. It can be distinguished from all congeners by presence of one or more rows of large ocellated spots above the base of the anal-fin, but...

Given its eventual size and natural behaviour this species is largely unsuitable for the home aquarium, and we know of only a handful of private aquarists with the facilities required to house it long-term. Unfortunately juveniles are readily available in the trade, although the scarcity of privately-maintained adults would suggest that most fail to reach their potential.

This species is distinguished from its Australian congeners S. jardinii and S. leichardti by possessing a lower number of lateral line scales (21-26 vs 32-36). It occurs naturally in a number of colour forms of which three were elevated to distinct species status in 2003, but the current majority view is that all represent S. formosus pending a detailed review. Kottelat (2013) mentions that the red form may...

Although S. leichardtii superficially resembles its Asian cousins, it is not considered as desirable an aquarium inhabitant, nor is it classed as being at risk in nature. It can be easily distinguished from the asian species by its much smaller scale size, greater lateral scale count (32-35 as opposed to 21-25 in the asian aros) and duller patterning. It differs from its Australian relative S. jardinii by its spotted scales, forward-pointing barbels, lack of sloping head and unpatterned gill cov...

This species' distribution is unclear although individuals from the aquarium trade are said to have been collected in the Tenasserim river basin in Tananthayi Region, southern Myanmar. Type locality is 'supposedly from Tananthayi district, Tananthayi River basin, obtained dead from aquarium fish vendor at Meik'.