Cardinal tetra

Overview

The cardinal tetra (Paracheirodon axelrodi) is the neon’s flashier cousin — the same electric-blue line, but with a band of brilliant red running the entire length of the body rather than just the rear half. In a large shoal against dark substrate and planting, cardinals are one of the most beautiful freshwater fish you can keep. They’re a little more demanding than neons, preferring warmer, softer, more acidic water and a well-established tank, which nudges them into intermediate territory.

Tank & water

Cardinals reward stable, soft-water conditions and numbers:

• A cycled tank of at least 60 litres — cycle the aquarium fully and add cardinals only to a mature system, several weeks in.
• Temperature 24–28 °C with a steady heater; they like the warmer end of the range.
• Soft, acidic water (pH 4.5–6.5). Botanicals and gentle filtration help create the blackwater conditions they evolved in. If your tap water is hard, read how to raise or lower pH.
• A dark, planted layout — live plants and dim lighting intensify their colour.

Feeding

Cardinals are omnivores that take small foods eagerly. Base the diet on a fine micro-pellet or crushed tropical flake, and offer frozen or live daphnia, baby brine shrimp and cyclops for condition and colour. Feed lightly, once or twice a day. See our fish food hub and best fish food picks for small-grain options.

Tankmates

Peaceful and mid-sized among tetras, cardinals mix well with other calm soft-water community fish — rummynose tetras, ember tetras, small rasboras, corydoras, dwarf cichlids and shrimp. Avoid large, boisterous or nippy species, and anything with a mouth big enough to eat them. A single-species shoal or a soft-water community built around them shows them off best.

Build a mature, soft, planted tank — our best aquarium for beginners and best nano aquarium guides help — and cardinals are a jewel-bright, peaceful centrepiece.