Cardinal tetra

Is Cardinal tetra a good aquarium fish?

Cardinal tetra reaches about 4.5 cm as an adult, so plan around the adult fish rather than the juvenile size seen in shops. The suggested minimum of 20 US gallons assumes suitable filtration, open swimming space and routine maintenance.

Generally peaceful in a suitable community. Keep the recommended group of at least 8 fish and avoid mixing it with tank mates that need a very different temperature, water chemistry or swimming level.

Water and aquarium setup

A stable temperature of 23–29°C and pH of 4.5–7.5 are the working ranges in the planner. Stability and clean, oxygenated water matter more than chasing a single target number.

Use plants, wood or rock to create cover while leaving the open swimming space this species needs.

Diet

Small community-fish pellets or flakes, supplemented with frozen or live foods.

Compatibility notes

Prefers warmer water than neons.

Use the Stocking & Bioload Planner to check a proposed community. Its estimated bioload value for one adult cardinal tetra is 0.69 units; this is a planning heuristic, not a replacement for testing nitrate.

Common mistakes

• Planning around the shop size instead of the adult size.
• Adding a schooling fish in a group smaller than its social minimum.
• Ignoring the tank's length, floor area or lid because the gallon number looks adequate.
• Adding fish before the aquarium is cycled and ammonia and nitrite are consistently zero.

Care ranges are conservative summaries of commonly cited husbandry references. Individual fish, strains and local water can differ; monitor the aquarium and adjust the plan gradually.