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Neolebias ansorgiiAnsorge's Neolebias
authority not recorded
Max length35mm SL1.4in SLTank45 × 30cm18 × 12inTemp24–28°C75–82°FpH5.0–6.0This species is rarely offered for sale and often appears to be a fairly plain fish when it is seen in dealer's tanks. However, when kept in the correct conditions it is a stunning little fish that comes highly recommended.

Neolebias trilineatusThree-lined Neolebias
authority not recorded
Max length35mm SL1.4in SLTank45 × 30cm18 × 12inTemp23–26°C73–79°FpH6.0–7.2This species is rarely seen in the trade but makes a superb addition to the smaller community tank. Often appears quite bland in dealer's tanks but, in the correct environment, is a stunning little fish....

Neosilurus brevidorsalisShortfin Tandan
Günther, 1867
Max length200mm SL8in SLTank120 × 45cm48 × 18inTemp20–28°C68–82°FpH6.0–7.5Type locality is ‘Nicol Bay, Cape York, Queensland, Australia’, and this species is restricted to the tips of northern Australia and southern Papua New Guinea. In Australia records exist only from the Jardine and Jackson river systems on the Cape York Peninsula, while in Papua New Guinea it’s known from the Fly River plus some other drainages.

Nimbochromis livingstonii
authority not recorded
Max length250mm SL10in SLTank120 × 45cm48 × 18inTemp24–28°C75–82°FpH7.6–8.8Not a fish for the general Malawi cichlid community, N. livingstonii is an ambush predator in nature, often being seen hanging motionless around rocky structures, in Vallisneria thickets or on the floor of the lake. It is a sedentary species and does not move around a lot. This is a behavioural adaptation known as thanatosis, or 'playing dead'. This strategy is usually used as for defensive means in other animals but in N. livingstonii is adapted for offensive means. The fish has a mot...

Nimbochromis venustusVenustus
authority not recorded
Max length250mm SL10in SLTank120 × 45cm48 × 18inTemp24–28°C75–82°FpH7.6–8.8Not a fish for the general Malawi cichlid community, N. venustus is an ambush predator in nature. It is often found hanging motionless around rocky structures, in Vallisneria thickets or on the floor of the lake. It is a sedentary species and does not move around a lot. This is a behavioural adaptation known as thanatosis, or 'playing dead'. This strategy is usually used as for defensive means in other animals but in N. venstus is adapted for offensive means. The fish has a mottled col...

Niwaëlla delicataAjime Loach
Niwa, 1937
Max length110mm SL4in SLTank90 × 30cm36 × 12inTemp20–24°C68–75°FpH6.5–7.5During winter months N. delicata retreats to streams or underflows where it remains dormant between October and April (Kano, 2000) before emerging to spawn. Other species living alongside it in nature include Rhinogobius flumineus, Cottus pollux and Phoxinus spp. Niwaëlla is closely related to Cobitis and N. delicata, also the type species, was described as C. delicata (Niwa, 1937). The combination of characters used to tell it...

Nothobranchius eggersi
Seegers, 1982
Max length50mm SL2.0in SLTank45 × 30cm18 × 12inTemp20–24°C68–75°FpH7.0–8.2Type locality is 'Rufiji River near Utete, eastern Tanzania', and this species is apparently endemic to the lower Rufiji including the Selous Game Reserve and freshwater parts of the Rufiji delta region. Populations in the aquarium hobby include 'Rufiji river camp', 'Kikongono', 'Ruhoi River', 'Kanga', 'Utete', 'Saadani Game Reserve', 'Ruvu River', 'Bagamoyo', 'Makurunge', 'Killimani', 'Chamakwese', 'Nyamwage', 'Mohoro', and 'Ukuni'.

Nothobranchius foerschi
Wildekamp & Berkenkamp, 1979
Max length♂ 55 · ♀ 40mm SL♂ 2.2 · ♀ 1.6in SLTank45 × 30cm18 × 12inTemp20–24°C68–75°FpH6.5–7.5Inhabits ephemeral, water-filled depressions, pools and swamps mostly located in lowland floodplains. Water levels in these seasonally-variable habitats typically decrease during the dry season and eventually become completely dessicated for several months each year. Near Bagamoyo it's been collected from pools of a flat, grassy floodplain alongside the congeners N. annectens, N. janpapi and N. melanospilus, while at Soga it occus together with N. janpapi and N. ocellatus. Most habitats appear to be heavily overgrown with terrestrial vegetation.

Nothobranchius rachoviiBluefin Nothobranch
Ahl, 1926
Max length55mm SL2.2in SLTank45 × 30cm18 × 12inTemp20–24°C68–75°FpH6.0–7.5Described from close to the city of Beira, Mozambique and for many years thought widely-distributed between the Kruger National Park, South Africa to the Kwa-Kwa River north of the Zambezi delta. Populations from the south and north of this range exhibiting differences in colour pattern and morphology have now been described as N. pienaari and N. krysanovi, respectively, meaning N. rachovii sensu stricto is restricted to the area between the lower Pungwe and Zambezi river basins in eastern Mozambique.

Notopterus notopterusBronze Featherback
Pallas, 1769
Max length600mm SL24in SLTanknot recordedTemp20–28°C68–82°FpH6.0–8.0This 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.

Oliotius oligolepisCheckered Barb
Bleeker, 1853
Max length45mm SL1.8in SLTank75 × 30cm30 × 12inTemp18–25°C64–77°FpH5.5–7.5This species is also traded as 'checker barb', 'checkerboard barb', or 'island barb', and is among the most ubiquitous species available in the aquarium trade. It is farmed commercially in enormous numbers with wild examples rarely, if ever, available. It was formerly included in the polyphyletic catch-all genus Puntius which contained over 100 species, but this situation has been largely resolved since the turn of the century.

Ompok bimaculatusButter Catfish
authority not recorded
Max length450mm SL18in SLTank180 × 60cm72 × 24inTemp20–26°C68–79°FpH6.0–8.0This infrequently seen (in the trade) species is also known as the two spot glass catfish, for fairly obvious reasons. It is more than likely that a number of separate species are currently considered within this one, as there are clear morphological differences between populations. Pending a taxonomic revision, these currently all remain classified as O.bimaculatus. This would also seem to explain the apparent toleration of the fish to wildly different water chemistry. Xanthic and albino forms ...

Ompok eugeneiatusBorneo Glass Catfish
authority not recorded
Max length165mm SL6in SLTank120 × 30cm48 × 12inTemp20–28°C68–82°FpH6.0–7.0Not often encountered in the hobby, but makes an ideal schooling catfish for a community of medium to large peaceful fish.

Ophthalmotilapia boops
authority not recorded
Max length150mm SL6in SLTank120 × 38cm48 × 15inTemp23–27°C73–81°FpH7.5–9.0This was the first species to be placed into the genus Ophthalmotilapia.

Ophthalmotilapia nasuta
authority not recorded
Max length200mm SL8in SLTank150 × 45cm60 × 18inTemp23–27°C73–81°FpH7.5–9.0O. nasuta can be distinguished from other members of the genus primarily by the fleshy proboscis-like growth that extends beyond the upper lip. It exists in several different geographical morphs including "Kachese", "Mpimbwe", "Cape Tembwe" and "Chamba", among others. These should not be mixed in aquaria as they will hybridise freely....

Ophthalmotilapia ventralis
authority not recorded
Max length150mm SL6in SLTank135 × 45cm53 × 18inTemp23–27°C73–81°FpH7.5–9.0This is a truly stunning species that does well in a Tanganyikan community with well-chosen tankmates. It exists in well over 20 colour morphs, too many to list here. Obviously these should not be mixed in aquaria as they will hybridise freely. In nature, it is only the largest dominant males that build nests whilst the subdominant males and females shoal together. The territories of these dominant fish may measure several metres across....

Opsarius barna
Hamilton, 1822
Max length130mm SL5in SLTank150 × 60cm60 × 24inTemp16–24°C61–75°FpH6.0–8.0This species occasionally appears in the ornamental trade, usually as 'striped hill trout' or 'banded hill trout'. It can be distinguished from congeners by the following combination of characters: lateral line complete with 40-42 scales; barbels absent; 10-13 anal-fin rays; body with 9-11 dark blue vertical bars; last dorsal-fin ray extending to caudal-fin base.

Opsarius bernatziki
Koumans, 1937
Max length90mm SL3.5in SLTank120 × 45cm48 × 18inTemp18–26°C64–79°FpH6.0–7.5Type locality is ' Kapa, northwestern peninsular Thailand', which may refer to modern-day Kapoe district, Ranong province, and additional records exist from other localities in Ranong as well as Phang-nga and Pattani provinces. Although the precise extent of its distribution is unclear it appears to occur in river systems on both sides of the Tennaserim Hills in pen...

Opsarius caudiocellatus
Chu, 1984
Max length86mm SL3.4in SLTank150 × 45cm60 × 18inTemp18–24°C64–75°FpH6.5–8.0This species may have appeared in the aquarium trade though probably not under the correct name. It can be told apart from similar-looking congeners by the following combination of characters: presence of a black round spot at the caudal base; dorsal-fin rays black with connecting membranes transparent; posterior dorsal-fin origin located midway between upper angle of gill aperture and caudal-fin base, or slightly closer to the latter.

Opsarius dogarsinghiManipur Baril
Hora, 1921
Max length85mm SL3.3in SLTank150 × 60cm60 × 24inTemp18–24°C64–75°FpH6.0–7.5Described from 'Etok stream near Chanderkhong, southern watershed of the Naga Hills, Manipur, Assam', located within the Chindwin River basin in northern India. The Chindwin is the major tributary of the Ayeyarwady/Irrawaddy River and most of it flows within Myanmar although two of its own tributaries, the Manipur and Yu rivers, originate in the Indian states of Manipur and Nagaland.