How Many Cardinal Tetras in a 29 Gallon Tank?
About 11–15 — based on adult size, bioload, and real water volume.
In a 29-gallon tank you can comfortably keep about 11–15 cardinal tetra — enough for a proper school, on their own with good filtration and regular water changes. Add fewer if you're mixing in other species.
How we get that number
An adult cardinal tetra reaches about 2.0" and has a low bioload. Working from real water volume and waste output (not the old one-inch-per-gallon myth), a 29-gallon tank supports roughly 11–15 of them. Because cardinal tetra are schooling fish, keep them in a group of at least 6 — never just one or two. They need 73–81°F water at pH 5.5–7.
Build your exact stocking with the calculator → Full cardinal tetra care guide →
Gear for a 29-gallon tank
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