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Fish, Shrimp & Corals


December 13, 2018 | By Oliver Lucanus

No other aquarium fish is as popular, or as recognizable, as the CARDINAL TETRA. Since it was first brought back to the USA by an American Airlines pilot in the 1960s, the fish has been a favourite in community tanks worldwide.

Neon tetras consist of 3 species:

COMMON NEON TETRA (Paracheirodon innesi) is found in clear water and white water lagoons, as well as streams in the lowlands of the Orinoco and Amazon basin.

CARDINAL TETRA (Paracheirodon axelrodi) is restricted to clear and black water habitats in Brazil’s upper Rio Negro and middle Orinoco in Colombia and Venezuela.

“FALSE NEON” TETRA (Paracheirodon simulans) is smaller and lives in the upper portions of the same stream.

These three species are quite easily distinguished. The cardinal tetra has the brightest red belly. The neon tetra has only one red stripe near the base of the tail over the anal fin. The false neon tetra has very little red, not to mention a more slender body (the iridescent blue is also more green than the other two species).

The common neon tetra is bred in large numbers in Southeast Asia, Florida and the Czech Republic, including some longfin, platinum and even deformed variants. Very few of the neon tetras sold today actually still come from the Amazon. The cardinal tetra, on the other hand, is still collected in the wild for the most part. For breeders, it is a much greater challenge to reproduce than the common neon. By export volume, it represents nearly 80% of the tropical fish exports from Brazil, and a significant part of the volume from Colombia. Nearly 1.5 million cardinal tetras are exported monthly to North America alone!


Before questioning if these numbers cause harm to the environment, or the species, we have to take a closer look at the sustainability of our hobby.

First off, cardinals are collected by artisanal fishermen, with small nets that look like long snowshoes, and are scooped from streams about fifty or so at a time. The fishermen have to use their own boats, gasoline and equipment, so they will only collect from those streams that are within easy transport distance back to the dealer.

Unlike many other jobs in the Amazon (i.e. logging, gold mining, etc.), the ornamental fish trade is earning money in a much more sustainable way, and has a high vested interest in protecting the environment from such other industries to ensure the fish supply is constantly renewed.


The small streams are usually very shallow in the dry season, and the cardinals live in small troops or larger flocks at a depth of about 12”-32”.

These habitats are shared with a number of other popular aquarium fish such as pencil fish, rummynose tetras, hatchetfish, checkerboard cichlids, Apistogramma dwarf cichlids, and Corydoras. Predators include pike cichlids, leaf fish and barracuda characins.


Cardinal tetras have a reputation of being a sensitive fish. In reality, they are just as hardy as other tetras providing some very basic rules are followed.

This begins from the point of purchase. Cardinal tetras are shipped over long distances to export points in Manaus (Brazil) and Bogota (Colombia). From there, they travel another day or more to reach your local wholesaler or retailer.

At least one week in quarantine is needed to make sure the cardinals recover from their journey, during which time they are not fed. Cardinals must not only be treated for bacterial disease caused by bad water conditions in transport, but they must also be fed frequently to regain their rounded stomach form.

To ensure the fish you are buying are ‘ready’ to bring into your home aquarium, you should follow these basic rules:

The stomach must be convex, not concave. Starved fish have little or no resistance to disease and should never be sold.

Avoid buying from an aquarium where the fish seem to sit still, are not moving in a school or have even one dead tank mate. Unlike neons, cardinals are fish that should be in motion. Tapping the glass near the top should prompt the fish to come to the surface looking for food.

Never buy cardinals if they show white patches near the dorsal fin, or white tips on their tails. Flexobacter is a bacterium that can affect all tetras. In farmed fish, it is a real problem because the disease breaks out when they become stressed during transport.

Cardinals are also sensitive to Ich (White spot disease), which is easily identified and should be avoided at all costs. A reputable fish retailer should not offer fish with white spots for sale, however, I recommend you always check the fish yourself first whenever possible.


Some other basic rules can also be applied to the home aquarium:

First, cardinal tetras need good water quality. A 50% water change the day before you bring home any new fish is always a good idea.

Avoid placing your cardinals with predatory fish such as larger cichlids, larger gouramies and angelfish. Cardinals, like most tetras, sleep at night and become easy prey for the cichlids. Some barbs are good tank mates, but many (i.e. tiger barbs) can outcompete cardinals for food and cause too much stress with their aggression.

Choose tank mates carefully, and stay with species that reach less than 2 inches in total length. The ideal tank mates for cardinals, as well as neons, are other small tetras such as Corydoras, dwarf cichlids, dwarf gouramies, and Otocinclus.

Once settled in, cardinals are hardy and beautiful community fish that can live up to 8 years, growing close to 2 inches in total length.


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