Tank Size and Water Parameters
Cardinal tetras are active swimmers that need a minimum 20-gallon tank to accommodate their schooling nature. A larger tank (30+ gallons) is better for a bigger school. They require soft, acidic water with a pH of 5.0-6.5 and hardness below 4 dGH. Temperature should be 73-81°F (23-27°C). Use a sponge filter for gentle flow. Keep the tank heavily planted with driftwood and leaf litter to mimic their Amazonian habitat. Perform weekly 25% water changes with RO/DI water remineralized to target parameters.
Diet and Feeding
Cardinal tetras are omnivores with a small mouth. Feed a varied diet: high-quality micro pellets or flakes as staple, plus small live or frozen foods like baby brine shrimp, daphnia, and microworms. Offer food 2-3 times daily in small amounts they can consume in 2 minutes. Avoid overfeeding to prevent water quality issues. Include vegetable matter like spirulina flakes occasionally.
Tank Mates and Compatibility
Cardinal tetras are peaceful but can be stressed by large or aggressive fish. Ideal tank mates include other small South American species: dwarf cichlids (Apistogramma), pencilfish, hatchetfish, Corydoras catfish, and small plecos. Avoid fin-nippers like tiger barbs or very large cichlids. Keep them in groups of at least 6, preferably 10+, to encourage natural behavior and reduce stress.
Health Care and Common Issues
Cardinal tetras are sensitive to poor water conditions. Common issues include ich (white spots) and fin rot. Maintain stable water parameters and quarantine new fish for 2 weeks. If you notice flashing, scratching, or lethargy, test water immediately. For disease signs, consult a licensed veterinarian. Do not medicate without accurate diagnosis. A healthy cardinal tetra lives 3-5 years with proper care.
Key Takeaway
Provide a 20+ gallon planted tank with soft acidic water, a school of 6+ cardinal tetras, and a varied diet for optimal health.