Can rummy nose tetras live with black neon tetras?

Verdict
Yes

Yes, rummy nose tetras and black neon tetras can live together. Both are fine at 75–81°F. Plan on at least 20 gal.

Rummy nose tetraRummy nose tetra75–84°F · pH 5.5–7 Black neon tetraBlack neon tetra73–81°F · pH 5.5–7.5

Why it works

Water side by side

55°60°65°70°75°80°85°90°Both: 75–81°Rummy nose tetra 75–84°Black neon tetra 73–81°
The green band is the temperature range both can live in.
456789Both: 5.5–7Rummy nose tetra 5.5–7Black neon tetra 5.5–7.5
The green band is the pH both tolerate.

Size to scale

Rummy nose tetra · 2 inBlack neon tetra · 1.5 in0"1"2"3"4"5"6"
Adult length in an aquarium. A fish can swallow anything that fits in its mouth, roughly a third to half its own length for predators.

Care at a glance

Rummy nose tetraBlack neon tetra
Temperature75–84 °F73–81 °F
pH5.5–75.5–7.5
Adult size2.0 in1.5 in
Minimum tank20 gal15 gal
TemperamentPeacefulPeaceful
Swims atMiddleMiddle
GroupGroups of 6+Groups of 6+
DietOmnivoreOmnivore

Better tank mates for rummy nose tetras

All rummy nose tetra tank mates

Better tank mates for black neon tetras

All black neon tetra tank mates

Questions

Can rummy nose tetras live with black neon tetras?

Yes, rummy nose tetras and black neon tetras can live together. Both are fine at 75–81°F. Plan on at least 20 gal.

What temperature suits both rummy nose tetras and black neon tetras?

75–81 °F. Rummy nose tetras need 75–84 °F, black neon tetras need 73–81 °F.

What size tank do rummy nose tetras and black neon tetras need together?

At least 20 gal, set by the rummy nose tetra. Add space for each extra fish.