Cardinal Tetra (Paracheirodon axelrodi) - Tank Raised

The Cardinal Tetra (Paracheirodon axelrodi) is the fish people picture when they picture a planted tank. A band of electric blue runs the length of the body with a deep crimson stripe beneath it, and in a school of a dozen against dark substrate and green plants there is genuinely nothing better looking for the money. These are tank raised and graded medium to large, so they are past the fragile stage and already coloured up. Browse the rest of our freshwater fish.

Cardinal or Neon? Look at the Red

These two get mixed up constantly, and the difference is easy once you know it. On a Cardinal Tetra the red stripe runs the entire length of the fish, nose to tail. On a Neon Tetra the red only covers the back half, from mid-body to the tail. Cardinals also get a little larger, hold their colour better as adults, and prefer slightly warmer water.

Why Tank Raised Matters Here

Wild Cardinals come out of Amazon blackwater that is soft and acidic, and they can sulk or fail in ordinary hard tap water. Tank-raised fish are bred and grown in normal aquarium conditions, so they take average tap water without complaint, eat prepared food from day one, and arrive carrying far fewer parasites. For most people this is the difference between a school that thrives and a school that slowly disappears.

Care Guide

• Buy a real school: six is the bare minimum, ten or more is where they actually behave like Cardinals. In small numbers they hide, stay pale, and stress. In a proper group they hold the open water and colour up hard.
• Tank size: 20 gallons and up for a school of ten. Length matters more than height.
• Water: 75 to 82°F, pH 6.0 to 7.5. They like it a touch warmer than Neons. Tank-raised stock is tolerant of moderately hard water, but stability beats chasing numbers.
• Aquascape: dark substrate, planted background, and some driftwood. Colour is partly behavioural, and a fish that feels covered shows far more red and blue than one in a bare bright tank.
• Diet: small mouths. Crushed flake, micro pellets, frozen daphnia, baby brine, and frozen bloodworms. Feed small amounts once or twice a day.
• Temperament: completely peaceful. They will not bother anything, including shrimp and snails.
• New tank caution: Cardinals are sensitive to unstable water. Add them to a cycled, settled aquarium rather than a brand new one.

Specifications

Compatibility

Ideal in a peaceful planted community: corydoras, other small tetras such as Rummynose and Von Rio Flame Tetras, rasboras, small rainbowfish, honey gouramis, and bristlenose plecos. Completely safe with Amano Shrimp, nerite snails, and live plants.

Avoid anything with a mouth big enough. A two-inch Cardinal is a snack for an adult angelfish, an oscar, or a larger cichlid, and it will get picked off eventually even if the two coexist at first. Also skip known fin-nippers like tiger barbs and serpae tetras.

Recommended Foods & Supplies

• Ocean Nutrition Freshwater Community Flake, crushed small, as the daily staple
• Frozen daphnia, baby brine shrimp, or bloodworms a few times a week for colour
• Amazon Sword and other live plants for cover, which is what brings the colour out
• Seachem Flourish to keep those plants going

FAQ

What does "fresh out of QT" mean?
Every fish we bring in spends time in our in-store quarantine before reaching the sales floor. We observe it, treat preventatively, and confirm it is eating prepared food. These just graduated, so they are settled and feeding rather than straight out of a shipping bag.

How is this different from a Neon Tetra?
The red stripe. On a Cardinal it runs the full length of the body; on a Neon it covers only the back half. Cardinals also grow slightly larger and prefer marginally warmer water.

How many should I buy?
Six minimum, ten or more if the tank allows. This is not upselling. Cardinals are a schooling fish and a group of three will hide in the corner and look washed out.

Do I need soft acidic water?
Not with tank-raised fish. Wild Cardinals want blackwater conditions, but these were bred and raised in ordinary aquarium water and do fine in typical tap. Keep it stable and clean.

Why do they look pale in the bag?
Stress and bright light both wash the colour out temporarily. Give them a settled planted tank with darker substrate and the red and blue come back within a day or two.

Are they safe with shrimp?
Yes. Adult shrimp are ignored entirely. Very small shrimplets may occasionally get eaten, as with any small fish, but a planted tank with moss gives them cover.