Tetra Care: The Essentials
Fish
Beastly Facts · Updated
The small schooling fish that share one set of rules and differ on almost every number!
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Did you know? Neon and cardinal tetras are easy to mix up in a shop tank, but the cardinal's red stripe runs the full length of its body, where the neon's covers only half of it.
Tetra is a common name rather than one scientific group. The word is short for Tetragonopterus, an old genus name, and it now covers small characins spread across several families in South and Central America, Mexico and Africa. Most South American tetras come from soft, acidic streams, either clear or stained the color of tea, and many characins keep their salt balance in water that acidic. They school mainly for safety: when a predator appears, neon tetras move toward the middle of the group, where any one fish is least likely to be the one caught.
Pick your tetra
Same rules, different numbers. The figures under each species come from its own guides, and the row opens its full care guide.
Neon Tetra
The tiny electric-blue schooler that turns any planted tank into a shimmering river scene!
- Tank
- 24-inch tank for 10
- Temp
- 70 to 77°F
- pH
- 6.0 to 7.0
- Size
- 1 to 1.5 in
Cardinal Tetra
The neon tetra's flashier cousin, lit up red from nose to tail!
- Tank
- 20-gallon long for 10
- Temp
- 73 to 84°F
- pH
- 5.0 to 7.0
- Size
- 2 in
Ember Tetra
The tiny orange schooler that glows like a coal against dark plants!
- Tank
- 10-gallon for 10
- Temp
- 75 to 82°F
- pH
- 5.0 to 7.0
- Size
- 0.8 in
Coming: Rummy-Nose Tetra, Black Skirt Tetra, Glowlight Tetra
Keeping tetras together
Which tetras can share one tank on water alone, worked out from the ranges above.
| Species | 1Neon | 2Cardinal | 3Ember |
|---|---|---|---|
| 1 Neon | Yes | Limits | |
| 2 Cardinal | Yes | Yes | |
| 3 Ember | Limits | Yes |
Yes: temperature and pH ranges overlap.
Limits: they overlap, but the shared temperature band is under 3°F, so a heater drifting a degree can take one species out of range.
All three together. Yes, but with limits: the warm end of the neon's temperature range, within its pH range.
What every tetra needs
School
Ten of one species. Groups of 10 shoaled the most in the group-size study, and ten of one species beats five each of two.
Aquarium Stocking and Tankmates →
Cycle first
Most fishless cycles finish in four to six weeks. No tetra goes in until ammonia and nitrite read zero.
Cycling guide →
Soft water
Every tetra here wants soft, acidic water. Work with what your tap gives you: dosing pH-up or pH-down against KH is how keepers crash a tank.
Freshwater pH, GH, and KH →
Food size
Tetra mouths are tiny, so micro-pellets or flake crushed fine. Food too large gets spat out, and the fish starve in a tank that looks fed.
Feeding guide →
Quarantine
At least 30 days in a separate tank before a new fish joins the school.
Quarantine guide →
Ich
86°F held for two weeks kills most strains, and it sits above every tetra here but one. Cardinals tolerate it in short spells, with strong aeration; for the rest, heat goes only to the top of their range and medication does the killing.
Treating Ich →
Water changes
25 to 30% weekly. Test nitrate first: under 20 ppm the routine is right, past 40 ppm the next change is 50%.
Aquarium Water Changes →
Power outage
Oxygen is the threat, not darkness. Unplug the filter rather than letting it sit dead in the water, and keep the surface moving.
Power outage guide →
Frequently Asked Questions
How many of a schooling fish do I need?
Six is the floor most species pages give, and the research points higher. In the group-size study behind that advice, neon tetras and white cloud mountain minnows showed the least aggression and darting in the larger groups, and groups of 10 shoaled the most. Ten of one species beats five each of two.
Can I treat ich with heat alone?
Only if your fish can live at 86°F for two weeks, because that is the temperature most ich strains cannot survive, and it must be held with extra aeration since warm water carries less oxygen. Discus can, and cardinal tetras tolerate it in short spells, so for them it is possible with strong aeration, watched closely. Goldfish, koi, zebra danios, neon, ember, rummy-nose, black skirt and glowlight tetras, and bristlenose plecos cannot, and for them heat goes only as high as the species ceiling, to speed the cycle, while salt or medication does the killing.
Can different tetra species school together?
Not as one school. Two neons, four embers and four cardinals are three small groups, each below the floor of six, rather than one school of 10. Give each species its own full school in a tank and water that suit all of them, or keep a single species.
How long does it take to cycle a fish tank?
Most fishless cycles finish in four to six weeks at a stable warm temperature, though a gene-sequencing study of real home aquarium biofilters found two tanks reaching undetectable ammonia and nitrite by week three while a third took until week eight. Cold water, no seeding, and an inconsistent ammonia dose all push a cycle toward the slower end of that range.
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