The range for ember tetras
Aim for 75 to 80 degrees Fahrenheit and a pH of 5.5 to 7.0. Ember tetras come from the Araguaia River basin in Brazil, where slow, tea-stained tributaries run warm and soft over leaf litter. In that water a healthy ember is translucent orange-red, like a coal seen through the glass; in hard or alkaline water the color thins to a washed pink and the fish never quite looks finished, however well it is fed.
Why small fish need slower hands
An ember tetra weighs almost nothing and lives in the nano tanks its size invites, and small volumes change fast: a degree of heater drift or a big top-off with mismatched water is a large event in five or ten gallons. Soft, slightly acidic water also buffers poorly, so pH can slide between changes if waste builds up. The answer is rhythm over heroics: small water changes done often, replacement water matched for temperature and roughly for pH, and feeding measured in pinches so little food decays.
Building the ember setup
Set the heater near 77 degrees and use a thermometer you trust, because inexpensive heaters can wander by more than this fish appreciates. Dark substrate, floating plants to soften the light, and a gentle filter outflow recreate the shaded stream edge embers prefer, and they will color up within days of feeling hidden enough. If your tap water is hard, blending in reverse-osmosis water gradually across several changes brings hardness and pH down without a sudden shift. Add embers in a proper school, since a handful of fish in open water stays timid and pale even at perfect numbers.
Color as your daily test kit
Keepers learn to read embers like a gauge: deep ember orange across the school at feeding time means temperature, acidity, and security are all in line. A school that fades after a water change is telling you the new water differed, and a school that fades slowly over weeks is usually living in water creeping harder or more alkaline than the test kit last showed. Retest, adjust gradually, and change one variable at a time so you know what helped.
Tankmates in an ember-sized world
Everything about ember care scales down, including the company. Tankmates must be small and peaceful enough that an inch-long fish is never a target or a meal: small rasboras, green neon tetras, pygmy corydoras, and shrimp all share an ember's soft, warm water without crowding it. Avoid fin-nipping barbs and boisterous danios entirely, since a stressed ember hides, pales, and stops feeding long before it is actually harmed. Keep the ember school itself generous, ten or more where the tank allows, because numbers are this species' security system. In a big, calm school the fish spread through the plants instead of clumping, and their color deepens across the whole group within days. For a school this small, checking before changing anything is the safeguard that matters. KinsLe's Kimmy can answer a follow-up question — she draws her answers from the KinsLe Answers library.