Family Characidae or American Tetras ( Characidae )
Genus Charax.
— Conde’s charax — Charax condei [Gery & Kroppel, 1976]. Synonym: Asiphonichthys condei. Venezuela, Brazil, Rio Negro. 5-7 cm. This fish is notable for its remarkably translucent body. Its body is yellow-brown with small dark brown speckles on the back that sometimes merge into stripes. A greenish-yellow lateral band runs along the sides, terminating at each end in a round black spot—one positioned right near the head, and the other at the base of the caudal fin. Under reflected light, the entire body sparkles like tiny diamonds. The lower jaw is white.
Fins are colorless. The anal fin is very long, extending from the base of the abdomen to the caudal peduncle. Males have a longer dorsal fin, and during the breeding season their throat turns orange; females have a more arched back. Translucency is especially pronounced in juveniles. With age, it disappears completely in fully grown fish. Under stressful conditions, the fish loses its coloration.
The aquarium should be densely planted, as the fish continually lingers in dense thickets waiting for prey. It frequently stands motionless among aquatic plants. Provide ample shaded shelters among driftwood and rocks. Dark decor and subdued lighting are preferred. It is considered a micro-predator, making it unsuitable for a community tank with small fishes. Keep them in a small shoal of at least six individuals. A peculiar habit is its tendency to hover head-down. It can remain in this position for hours before swimming. Substrate should preferably be dark.
Water should be soft and acidic. These fish are very sensitive to sudden changes in water parameters; introducing them into a mature aquarium with low nitrate and phosphate levels is recommended, as they are susceptible to them. Fish fry make the best food, though they also accept bloodworms. Feed primarily live foods, as well as frozen and dry preparations. pH 6.0-7.5; dH 3-10°; T 23-25°C.
— Humpbacked charax — Charax gibbosus [Linnaeus, 1758]. Synonyms: Cynopotamus gibbosus. (Common names: Glass Headstander, Humpback Headstander, Transparent Tetra). Brazil, Guyana, and Paraguay; central and lower Amazon River basin, Paraguay River, Rio Negro. 15 cm, females smaller. Coloration depends on lighting and fish age. The body is elongated with a very high back that rises sharply directly behind the eyes.
The body of this fish is beige-gray with fine silvery scales and is translucent, allowing internal organs and skeleton to be clearly seen. It possesses a dark black humeral spot and a second spot at the base of the caudal fin. The back is humped, and the eyes are large. Fins are transparent. Males turn pale yellow during spawning, while females become very plump.
They look best in a densely planted aquarium kept in a shoal of 6 or more specimens; they are more active at night. Fish kept in pairs tend to be sluggish and secretive. They swim head-down and frequently hover among plants. Water must be soft and acidic. It is a small predator feeding on small fish and aquatic insects. In the aquarium, feed mostly live foods, though frozen and dry foods are also accepted. pH 6.0-7.5; T 24-27°C; dH up to 25°.
Genus Phenacogaster.
Also kept in aquaria: — Phenacogaster pectinatus (Cope, 1870) — Glass phenacogaster. Amazon basin. 5 cm. Transparent fish; — Phenacogaster apletostigma (Lucena & Gama 2007). Brazil. Features a large, vertically elongated humeral spot extending from the lateral line near the dorsal fin;
— Calvert’s phenacogaster — Phenacogaster calverti [Fowler, 1941]. Synonym: Grammabrycon calverti. Paraguay, Brazil. 5 cm. A modestly colored yet interesting, small, peaceful species with a somewhat elongated anal fin. A small shoal can be kept in a tank of 60 liters or more with plenty of open swimming space, plants along the sides and back walls, and moderate lighting. Tank mates should be strictly peaceful fish. T 22-28°C; pH 6-7; dH 3-10°.
Genus Roeboides.
— Day’s roeboides — Roeboides dayi [Steindachner, 1878]. Synonyms: Roeboides caucae, magdalenae, meeki, romeroi. (Common names: Glass Sardine, Hunch Back Sardine). Brazil, Panama, Cauca River. 10 cm. Sandy with a silvery sheen, semi-translucent, with faint hatch marks across its deep body, a dark stripe along the spine, and a black spot near the swim bladder followed by a white-yellow spot; abdomen is silvery. Caudal fin has a black spot bordered by two small white marks. Other fins are transparent. In spawning condition, males develop a red throat. Males are significantly slimmer and smaller than plump females.
Aggressive species; considers smaller fish as prey and may scale-graze (eat scales off other fish). They prefer to stay near the edges of open areas along vegetation. Characteristic posture is stationary—either hovering or swimming slowly with the head slightly angled downward. They maintain distance from conspecifics, and solitary individuals readily claim a territory. Medium-grain sand substrate is suitable. Provide decorative rocks and driftwood to form hiding places. Strong filtration (a voracious eater) and oxygen-rich water are needed. Diet consists primarily of all kinds of live foods, along with frozen varieties and flakes. Fry are prone to cannibalism. Not recommended for beginners. pH 6.0-7.5; dH 10-20°; T 22-28°C.
— Guatemalan roeboides — Roeboides guatemalensis [Gunther, 1864]. Synonyms: Anacyrtus guatemalensis, Roeboides bouchellei. (Common names: Guatemalan Glass Characin, Guatemalan Headstander). From southern Mexico and Guatemala to Panama. 12-15 cm. Body coloration is yellowish with a silvery sheen, with a vertical dark dot at the base of the caudal fin. Fins are translucent light orange; the caudal fin has a reddish tint. Males feature a longer, more pointed dorsal fin edged in cream. The reddish caudal fin has a larger upper lobe than lower lobe, with a vertical dark bar at its base.
Peaceful toward larger fish, but will consume small tankmates. Requires a spacious aquarium with dense vegetation and dim lighting. Typical stance is motionless, hovering in place or swimming slowly head-down. A predator; juveniles are prone to cannibalism. Prefers fresh water at 22-25°C. Breeding is possible in large aquariums. Matures around 15 months of age. dH up to 15°; pH 7.0.
Genus Axelrodia, Genus Boehlkea, Genus Bryconella, Genus Bryconops, Genus Brittanichthys.
