Cardinal Tetra Fact Sheet
The Cardinal Tetra Paracheirodon axelrodi is closely related to the very popular Neon Tetra Paracheirodon innesi and the Green Neon Tetra Paracheirodon simulans. It is less closely related to the hundreds of other tetra species. The Cardinal’s specific name, axelrodi was given to honour the great fish expert, Herbert R. Axelrod. The Black Neon Tetra Hyphessobrycon herbertaxelrodi is not a very close relative of the Neon or the Cardinal. Its name is misleading.
The Cardinal Tetra’s maximum length is a little over 4cm. Cardinal Tetras are a peaceful community fish suitable for keeping with other small, peaceful fish. Common companions include other small tetras, small Rasboras, Guppies and other livebearers like platies and swordtails, as well as Corydoras catfish.
Cardinal Tetras are often kept successfully with discus and seem better able to tolerate the high temperatures Discus fish need than Neons. They are also a little bigger than Neons and less likely to be eaten by discus.
Fish I would not recommend putting with Cardinals include all large fish, Buenos Aires Tetras and Tiger Barbs. I have known cases where people have successfully kept Cardinals with some of the fish I just listed, but there is some danger if you attempt it. If you keep Angel Fish and Cardinal Tetras together, you need to accept the likelihood of the Angel Fish growing big enough to eat the Cardinals.
The Cardinal Tetra comes from the upper reaches of the Amazon River. This is a tropical area and The Cardinal Tetra is a tropical fish. Cardinals should have heated water, unless they can be kept in a room that never gets cold. The obvious way to heat the water is with an aquarium heater. I suggest setting the thermostat to 24̊ C.
The Cardinal comes from acidic and extremely soft water. This is the ideal water for them and is probably essential if you want to breed Cardinals. However, they can be kept successfully in water with Ph ranging from 5.0 to 7.4. They will tolerate moderately hard water for living in, but extremely soft water is needed if you want to attempt to breed them. When they are kept with mixed other fish in an aquarium, I recommend a Ph of about 7. Some cover like plants are beneficial for the fish.
Companions
Like many tetras, the Cardinal is a schooling fish and I recommend that at least five be kept together. A school of Cardinals in an aquarium is a surpassingly beautiful sight. When it is dark, the Cardinal losses its bright colours, but quickly regains them when it gets light again.
Although Cardinals will school with their own species for preference, if there are too few Cardinals to form a school they can school with Neons .
Other fish that The Cardinal Tetra is compatible with include the other Tetras, including Neon Tetras, Head and Tail Light Tetras, Black Widow Tetras Emperor Tetras and Glass Bloodfin Tetras. As well the other tetras, The Cardinal Tetra is compatible with the Danios including the Zebra Danio , White Cloud Mountain Minnows, Guppies, Endlers Guppies, Rasboras,and most barbs, as well as other small fish which are not excessively aggressive.
The Head and Tail Light Tetra is also happy with the Corydoras catfish, including Peppered Catfish, and with all the smaller loaches.
Food
Like many fish, Cardinal Tetras are naturally omnivores and will eat a wide variety of food in the aquarium. Flakes are the normal basic diet for them. I find they also benefit from dry fry food. They enjoy small live food like small wrigglers (mosquito larvae) and small crustaceans like daphnia. Frozen foods like blood worms are also good. Remember they are small fish. DO NOT OVERFEED.
Sources
Cardinal Tetra Fact Sheet
Is the Cardinal Tetra an Annual Fish in the Wild?
