Freshwater Fish‎ > ‎Tetra‎ > ‎

Paracheirodon axelrodi

Paracheirodon axelrodi
Cardinal Tetra
The cardinal tetra, Paracheirodon axelrodi, is a freshwater fish of the characin family (family Characidae) of order Characiformes. It is native to the upper Orinoco and Negro Rivers in South America.
Growing to about 3 cm (1.25 in) total length, the cardinal tetra has the striking iridescent blue line characteristic of the Paracheirodon species laterally bisecting the fish, with the body below this line being vivid red in color, hence the name "cardinal tetra". The cardinal tetra's appearance is similar to that of the closely related neon tetra, with which it is often confused; the neon's red coloration extends only about halfway to the nose, and the neon's blue stripe is a less vibrant blue, however.
The cardinal tetra is a very popular aquarium fish but is less widespread than the neon tetra because until recently it was difficult to breed in captivity. However, many breeders are now producing the fish; in most cases one can determine if the cardinal tetra is bred or wild caught due to damaged fins on wild caught specimens. Normally aquarists prefer to buy tank bred fish 
The fish might also be effectively an annual species and may have a lifespan of just a single year in nature. It lives for several years in captivity.
An entire industry is in place in Barcelos on the banks of Brazil's Rio Negro in which the local population catches fish for the aquarium trade. The cardinal fishery here is highly valued by the local people who act as stewards for the environment. It may be said that the local people do not become involved in potentially environmentally damaging activities, such as deforestation, because they can make a sustainable living from the fishery.
Perhaps due to their wild-caught origins, cardinal tetras tend to be somewhat delicate in captivity. In the wild, these fish inhabit extremely soft, acidic waters, but seem to be tolerant of harder, more alkaline water conditions; a greater concern is probably polluted tank water (including high nitrate levels.) They prefer warmer water temperatures (in the upper 70s F or warmer (20°C)), and will readily accept most forms of dry food. Captive-bred cardinals tend to adapt to hard water better than wild-caught cardinals.
P. axelrodi is also often called the red neon tetra. Cheirodon axelrodi (the original name) and Hyphessobrycon cardinalis are obsolete synonyms. The fish's common name, cardinal tetra, refers to the brilliant red coloration, reminiscent of a cardinal's robes. 
Given the origins of the cardinal tetra, namely blackwater rivers whose chemistry is characterised by an acidic pH, low mineral content and the presence of humic acids, the species is adaptable to a wide range of conditions in captivity, though deviation from the soft, acidic water chemistry of their native range will impact severely upon breeding and fecundity. The preferred temperature range of the fish is 21°C to 28°C (70°F to 82°F). The water chemistry of the aquarium water should match that of the wild habitat - filtration of the aquarium water over peat is one means of achieving this.
As the species is a shoaling species in the wild, groups of six or more individuals should be maintained in an aquarium. They will shoal with their close cousins neon tetras however, so a combination of these two species totalling at least six should suffice. Tank currents can help encourage shoaling behavior. The larger the numbers present in an aquarium (subject to the usual constraints imposed by space and filtration efficiency), the better, and large shoals in any case form an impressive and visually stunning display.
The species will feed upon a wide range of aquarium foods, though again, conditioning fishes of this species for breeding will usually require the use of live foods such as Daphnia.
Aquarium furnishings should be planned with some care. Live aquatic plants, as well as providing an additional biological filtration component that assists with nitrate management in the aquarium, provide an environment that resembles at least part of the wild habitat, and fine-leaved plants such as Cabomba are usually the plants of choice, though other plants such as Amazon Swordplants and Vallisneria are equally suitable for an aquarium housing the cardinal tetra. Floating plants providing shade will also be welcomed by the species: this is connected with the breeding of the fish, which will now be covered. A perfect biotope to promote breeding, would be lots of bogwood, a few live native plants, with dark substrate and subdued lighting with floating plants.
The species exists in a number of different colour forms or phenotypes. A "gold" and "silver-blonde" form exist in the Rio Negro drainage which have less blue in the longitudinal stripe. The normal form from the Rio Negro drainage has a blue stripe which extends to the adipose fin, while the Orinoco drainage phenotype has a stripe which stops posteriorly of the adipose. The Orinoco phenotype may represent a subspecies of P. axelrodi.

宝莲灯鱼又名新红莲灯鱼、日光灯鱼,是一种体长约 4 ~ 5 厘米、娇小纤细观赏鱼珍品。宝莲灯鱼体呈纺锤形,体侧扁,头和尾柄较宽,吻圆钝。其口、眼稍大,臀鳍延长,尾鳍叉形。宝莲灯鱼体色艳丽,背部呈黄绿色,腹部乳白色。最显著的特色是在体侧,从眼后缘到尾柄有一条较宽的明亮的蓝色纵带,纵带下方后腹部有一片红色斑块,十分醒目。在光照下,宝莲灯鱼全身闪烁着金属的光泽,游动时时而蓝色,时而绿色,极为美丽。