The Cardinal Tetra
(Paracheirodon axelrodi)
By Bill Gehan
First published in The Tank, Northeast Philadelphia Aquarium Society, November
2004
Aquarticles
The Cardinal Tetra is a small fish (full grown 5cm or 2 inches) and is brightly
colored. This fish comes from the very soft and acidic waters of the Amazon basin and its
tributaries, which are located in Brazil, Colombia and Venezuela. The Cardinal Tetra is
often confused with the Neon Tetra (Paracheirodon innesi). The visual difference
between the Cardinal Tetra and the neon tetra is the length of the bright red stripe that
travels across their bodies. The Cardinal Tetra's red stripe travels the entire length of
its body, while the neon tetra's red stripe travels only half way down its body.
The Cardinal Tetra is a freshwater tropical fish and likes warm (72- 79 degrees F),
soft (hardness less than 6 dGH) and acidic water (pH of around 6.0). The Cardinal Tetra is
a schooling fish and in my opinion should not be kept in groups of less than six. In
nature, schools of this type of fish number from a few hundred to thousands. Cardinal
Tetras are omnivorous and will eat small insects, crustaceans, plants and other small
fish.
The Cardinal Tetra is not a difficult fish to keep as long as your aquarium water is
kept close to the parameters listed above and you perform partial water changes of about
20% weekly. They prefer well planted aquariums and small, peaceful tank mates. Choose your
Cardinals' tank mates well because any fish whose mouth is large enough will eat them, and
this includes wild discus and angelfish. Some good tank mates for your Cardinals in my
opinion would be any dwarf Cichlid, domestic bred Angelfish or Discus, Hatchet fish or any
small Cory catfish. You can also keep your Cardinals with any small fish from around the
world that requires the same type of water parameters. Large school of Cardinal Tetras
swimming from one end of the aquarium to the other end is an impressive sight.
Be very careful in choosing the fish you buy; make sure they are healthy (not thin or
exhibiting signs of disease) and eating readily. Ask the people working in the fish
room,"How long have these fish been in the store?" "Are they eating well
and can you show me?" If the fish have been in the store for longer than a
week, are eating well and your quarantine tank has the correct water parameters, then buy
them. Keep your new fish in the quarantine tank for three weeks before introducing them to
an already populated tank.
Cardinal Tetras will gladly accept any live food they can fit in their mouths. My
Cardinal Tetras like live black worms, flake food and will nip at some of my aquarium
plants. These fish will also accept frozen foods like blood worms, beef heart, daphnia and
many others. You might want to try a variety of live and frozen foods to see what they
like. Be careful that whatever live food you feed them does not contain any parasites that
could harm your fish. Don't feed your Cardinals live or frozen adult brine shrimp since
they have little nutritional value. Baby brine shrimp would be ok to feed them since they
still have their protein rich yolk sacs.
Breeding Cardinal Tetras can be difficult and I don't know anyone personally who has
done it successfully. All of my Cardinals are wild caught fish. Male Cardinals are
generally slimmer than females who tend to have enlarged abdominal sections. I have read
articles that suggest in order to breed Cardinals the aquarium water must be acidic (pH of
6.0) and very soft (less than 3 dGH). Spawning usually occurs in the evening and the
female will lay up to 500 eggs. Promptly remove the parents. The eggs will usually hatch
with in 28 hours and the fry will become free-swimming around 4 days later. I will try
this method eventually when I can get more room to set up another tank.
Remember to always do a little research on the animals that you want to buy. It is
vital that you provide the necessary conditions (aquarium space, water conditions and
proper diet) for your animals to thrive - never buy a fish on impulse. I can't tell you
how many times that I have met people who have bought a cute little pacu or peacock bass
that they think will stay small but winds up growing to well over 3 feet in length!
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