Rummy-nose tetra
Petitella rhodostoma (Ahl, 1924) (formerly Hemigrammus rhodostomus)
Also known as: Rednose tetra, Rednosed tetra
This is the classic rummy-nose tetra-the one with the bright red "nose" and the crisp black-and-white tail that flashes when the whole group turns together. They're tight-schoolers, so a bigger group in a longer tank is where you really get that synchronized, hypnotic swimming. The red face also doubles as a little "health meter" since it tends to fade when they're stressed or water quality slips.
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Rummy-nose tetras exhibit bright red snouts and a striking blue-black stripe running laterally, with a translucent silver body.
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Quick Facts
Size
5.0 cm (2.0 in)
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
20 gallons
Lifespan
5-6 years
Origin
South America (lower Amazon and Orinoco basins)
Diet
Omnivore - quality flakes/micro pellets plus small frozen/live foods (daphnia, brine shrimp, bloodworms)
Water Parameters
23-28°C
5.6-7.4
0-6 dGH
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Calculate heater sizeCare Notes
- Keep rummy-nose tetras in a real group (8-12+). In small numbers they get jumpy, hide more, and their color looks washed out.
- They look best in a longer tank with open swimming space and some plants/wood around the edges; a dark substrate makes the red nose pop. Add a tight lid-when they spook, they can launch.
- Aim for soft, slightly acidic water: pH ~5.5-7.0, GH low, and keep it warm (about 25-28°C / 77-82°F). They hate swings, so do smaller, regular water changes instead of big random ones.
- Use them like a "water quality indicator": if the red nose fades, something's off (ammonia/nitrite, rising nitrate, temp swing, or stress). Don't ignore that-test and fix fast.
- Feed small foods they can nail easily: good micro pellets/flakes plus frozen/live stuff like daphnia, baby brine, and bloodworms. A couple small feedings beats one big dump that fouls the water.
- Great with other calm community fish-corydoras, small rasboras, pencilfish, peaceful dwarf cichlids, and non-nippy gouramis. Skip fin-nippers (serpae tetras, tiger barbs) and big mouthy fish that see them as snacks.
- Breeding is doable but fussy: they'll scatter eggs in fine-leaf plants or a spawning mop, and the adults will eat the eggs. Use very soft, acidic water and dim light, then pull the parents right after spawning.
Compatibility
Good Tankmates
- Other calm midwater schoolers (cardinals/neons, black neon tetras, ember tetras). They vibe together as long as nobody's a fin-nipper and the tank isn't overcrowded.
- Corydoras catfish (any of the common types). Total no-drama bottom crew, and rummys ignore them completely-great combo in a soft, clean-water community.
- Small peaceful plecos like bristlenose (Ancistrus). Good algae helper, keeps to itself, and doesn't stress the school out.
- Dwarf cichlids that aren't jerks-think apistos or a pair of rams in a planted tank with space. Rummys are fast enough to stay out of the way, just give the cichlids caves/territory.
- Peaceful gouramis like honey gourami (or a mellow pearl gourami in a bigger tank). They hang up top/mid and don't bother the rummys.
- Peaceful oddballs like otocinclus. They stick to glass and leaves, and rummys don't compete with them much for food if you feed properly.
Avoid
- Anything nippy like tiger barbs (and a lot of the 'barb-y' vibe fish). They'll harass the school and you'll see rummys stay pale and hide more.
- Big aggressive/boisterous cichlids (most Africans, oscars, green terrors, etc.). Rummys either become expensive snacks or get stressed into nonstop panic mode.
- Fin-nippers and pushy semi-aggressive stuff like serpae tetras (often), some larger danios, and similar 'always on' fish. Rummys want calm water and a chill vibe.
- Big predators like larger catfish, arowana-types, or anything that can fit a tetra in its mouth. If it can swallow it, eventually it will.
1) Where they come from
Rummy-nose tetras come from the Amazon basin—mainly blackwater tributaries with tea-colored water, leaf litter, and soft, acidic conditions. That “red nose” look is basically their mood ring: if they’re stressed or the water’s off, it fades fast.
If you want a quick read on tank health, watch their faces. Bright red = usually happy. Pale noses = something’s bugging them (often water quality or temperature swings).
2) Setting up their tank
These aren’t “tough it out” tetras. They do best in a stable, mature tank. I’ve had the best luck once a tank is fully cycled and has been running a while—rummy-noses punish new setups.
- Tank size: 20 gallons long is a great starting point, bigger is even easier
- Group size: 10–15+ makes them way more confident (and the school looks amazing)
- Temp: warm side, roughly 78–82°F (they sulk in cooler water)
- pH/hardness: they’ll adapt, but soft to moderately soft water keeps them looking and acting their best
- Filtration: steady flow is fine, just don’t blast them like a river tank
- Lighting: moderate; plants help them relax and bring out color
A sandy or fine gravel substrate works. Add plants (stems, crypts, floating plants), a few bits of wood, and some leaf litter if you like the look. They don’t need caves, but they love visual cover and open swimming lanes.
Keep a lid on the tank. They’re not the worst jumpers, but a startled school can launch.
They really don’t like “swingy” tanks. Big parameter shifts, missed water changes, or a mini-cycle will show up as pale noses and clamped fins.
3) What to feed them
Rummy-noses are easy to feed once they’re settled, but they’re small-mouthed and a little shy the first week or two. Think tiny foods, frequent small portions, and variety.
- Staple: quality micro pellets or fine flake (crush it if needed)
- Frozen: baby brine shrimp, daphnia, cyclops, finely chopped bloodworms
- Live (if you can): baby brine shrimp and daphnia get them fired up fast
- Extras: occasional veggie-based flake for balance (they’re not big plant eaters, but variety helps)
If new fish are hiding and not eating, dim the lights and feed small amounts twice a day for a week. Once they realize food appears regularly, they turn into little piranhas.
4) Behavior and tankmates
A healthy school is nonstop motion—tight formation, coordinated turns, and that classic black-and-white tail flashing. In small groups they get skittish and scatter; in bigger groups they settle down and act “right.”
- Great tankmates: other peaceful tetras, pencilfish, rasboras, small peaceful barbs, Corydoras, otos, peaceful dwarf cichlids (like rams/apistos in the right setup)
- Usually fine: calm gouramis, small plecos that aren’t jerks
- Skip: fin nippers, big/fast feeders that hog all the food, anything that sees them as snacks (large cichlids, big catfish), or super boisterous fish that keep them pinned in corners
They’re one of my favorite “dither fish” for shy setups. If the rummy-noses are calmly schooling in the open, everyone else relaxes too.
5) Breeding tips (if you want to try)
Breeding them is doable, but it’s a project—more like a weekend science experiment than “oops, free babies.” They scatter eggs and will absolutely eat them if given the chance.
- Use a separate breeding tank (10–20g) with a sponge filter and gentle aeration
- Soft, acidic water helps a lot; warmer temps also encourage spawning
- Give them something to spawn over/into: a mesh, marbles, or a thick clump of fine plants (Java moss works)
- Condition adults on live/frozen foods for 1–2 weeks
- Move a pair or small group in the evening; spawning often happens early morning
- Pull adults right after you see eggs (or as soon as spawning is done)
Eggs and fry don’t love bright light. Keep the breeding tank dim or cover the sides if you’re getting poor hatch rates.
Fry are tiny. Start with infusoria or a commercial fry food for egglayers, then move to baby brine shrimp once they can take it. Clean water matters a lot here—gentle, frequent small water changes beat big ones.
6) Common problems to watch for
Most rummy-nose “issues” are really tank issues. They’re sensitive fish, and they broadcast stress loudly with color loss and weird schooling.
- Pale red noses: usually stress, temperature too low, or water quality slipping (check ammonia/nitrite first, then nitrates)
- Hiding and not eating: new tank jitters, too small a group, or aggressive tankmates
- Ich outbreaks: they can be ich magnets after shipping stress—quarantine new fish if you can
- Rapid breathing at the surface: low oxygen, high temp with not enough surface agitation, or gill irritation
- Random losses in “new” tanks: unstable cycle or big parameter swings after water changes
If you ever see ammonia or nitrite above zero, treat that like an emergency with rummy-noses. They don’t have much patience for it—big water change, detoxifier if you use one, and figure out what caused the spike.
Match temperature and take your time acclimating them. I’ve had the smoothest introductions by keeping lights off, floating the bag to match temp, then drip acclimating if my water is much different from the store’s.
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