Neon Tetra and Cardinal Tetra are very similar in appearance and can be confused with one another. The easiest identifiable difference between the two fish is the red stripe on the fishes body.
The Cardinal Tetras red stripe on the lower half of the body will extend the full length of the fish from eye to tail.
The Neon Tetra red stripe on the lower half of the body will extend from mid-body to the tail.
Paracheirodon Innesi commonly known as the Neon Tetra has been in the Aquarium Trade much longer than Cardinal Tetra. First discovered in the Amazon Jungle in South America in 1934. Neon Tetras are the less expensive of the two species. Neon Tetras are smaller than Cardinal Tetra at about 2.5cm/1 inch.
Neon Tetras come from soft acidic water with a pH of 6.0 to 6.5 but generally adapt well in aquariums up to pH of 7.8.
Neon Tetras are a great addition to community tanks and are best kept in a school of 5 or more fish.
Paracheirodon Axelrodi commonly known as the Cardinal Tetra, has become a popular fish in the aquarium trade since being discovered in 1956. Although priced a little bit higher than the Neon Tetra, the Cardinal Tetra is in high demand due to the striking red stripe and bigger 5cm/2 inch size.
Cardinal Tetras prefer soft acidic water as the Neon Tetra does, however Cardinals are more sensitive to the higher pH levels.
Like the Neon Tetra, Cardinal Tetras should be kept in schools of 5 or more fish.
Both Neon Tetra and Cardinal Tetra originate from South America. However most of the fish sold in aquarium stores today are bred in captivity by farms and commercial breders.
Captive-bred fish usually are hardier and more tolerant of different water parameters than wild-caught fish.
Neon Tetra are found in the Amazon Tributaries of Brazil, Columbia and Peru. While Cardinal Tetra are found in the waters of the upper Orinoco and Negro Rivers of South America. Cardinal Tetra have been discovered in other waters but are likely to have been release accidentally.