Black neon tetra vs Flag tetra: can they live together?

Verdict: Compatible

Both are comfortable at 23–28°C (73–82°F).
A pH of 5.5–7.5 suits both.
Minimum tank for the pair: 75 L (20 US gal)

Side by side

	Black neon tetra	Flag tetra
Adult size	3.2 cm (1.3 in)	3.4 cm (1.3 in)
Minimum tank	75 L (20 US gal)	55 L (15 US gal)
Temperature	23–28°C (73–82°F)	22–28°C (72–82°F)
pH	5.5–7.5	5.5–7.5
Hardness	2–15 dGH (36–268 ppm)	5–15 dGH (89–268 ppm)
Temperament	Peaceful	Peaceful
Community tank	Excellent	Good
Care level	Easy	Moderate
Diet	Omnivore	Omnivore