Peridot tetra
Jupiaba acanthogaster
Peridot tetras exhibit a striking olive-green body with distinct horizontal black stripes and vibrant, iridescent fins.
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About the Peridot tetra
This is a small South American characin that does its best work in a real group - once you have a bunch of them together they stay active and hang in the midwater like classic dither fish. The neat little twist with this species is the spine-like pelvic bones that can stick forward along the belly, which is where the name comes from.
Also known as
Quick Facts
Size
5.5 cm SL
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
20 gallons
Lifespan
3-6 years
Origin
South America
Diet
Omnivore - small pellets/flakes plus frozen/live foods like daphnia, brine shrimp, and bloodworms
Water Parameters
22-27°C
6.5-7.5
2-15 dGH
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Calculate heater sizeCare Notes
- Keep them in a group; larger groups generally reduce stress and help schooling behavior. Avoid keeping them singly or in very small numbers.
- Give them length to swim: a 20 long works, 30+ gallons is even better for a proper school. Add plants or wood along the edges and leave open water through the middle so they can cruise.
- They occur in a range of natural conditions; habitat data from Mato Grosso do Sul sites where this species is observed includes neutral pH around 7.3–7.5. Keep them in stable, well-maintained water and avoid chronic nitrate buildup.
- Feed like a tiny piranha - small pellets/flakes daily plus frozen stuff (daphnia, brine, bloodworms) a few times a week. They eat hard and fast, so spread food across the surface so the shy ones get some.
- Good tankmates are other quick, midwater fish that can handle a little attitude: larger tetras, rasboras, rainbows, and peaceful bottom fish like corys. Skip long-finned slowpokes (bettas, fancy guppies, angelfish) because these guys will test those fins.
- They look great in slightly dimmer light with floating plants, and they color up more when they feel covered from above. A darker substrate also helps the green sheen pop.
- Watch for fin-nipping and stress-scrapes when they are under-schooled or cramped; it usually fixes itself with a bigger group and more space. Also keep an eye out for skinny fish at feeding time - the bold ones can hog everything.
Compatibility
Good Tankmates
- Other small, peaceful tetras that like to school (think rummynose, lemon, glowlight). Peridot tetras are easygoing, and a bigger mixed-tetra school keeps everyone confident and less spooky.
- Corydoras catfish (any of the common species). They hang on the bottom, never start drama, and they match the same calm community vibe.
- Small, peaceful Loricariids like otocinclus or a bristlenose pleco. They do their own thing, and peridots mostly ignore them.
- Peaceful dwarf cichlids like Apistogramma or German blue rams (in a planted tank with hiding spots). Peridots stay midwater and usually keep out of the cichlids' way, even when the dwarfs get a little territorial.
- Choose tankmates that tolerate similar water conditions; confirm water-chemistry overlap (especially hardness/pH) before mixing with livebearers like guppies/platies.
- Hatchetfish or other chill top-dwellers. Nice spacing - they own the surface, peridots take midwater, and you get a more natural looking community.
Avoid
- Anything nippy like tiger barbs or serpae tetras. Even if peridots are peaceful, persistent fin-nippers will keep them stressed and hiding.
- Big, pushy fish like larger cichlids (convicts, green terrors, oscars). Peridots are not built for that kind of attitude and can get chased, chewed up, or just outcompeted at feeding time.
- Really predatory or mouthy stuff like pike cichlids or big characins that see 'small tetra' as a snack. If it can fit them in its mouth, sooner or later it will try.
Where they come from
Peridot tetras (Jupiaba acanthogaster) come out of South America, where they live in warm rivers and tributaries with a decent amount of current, leaf litter, and overhanging plants. They are one of those fish that look plain in a dealer tank, then suddenly start flashing that green-gold sheen once they settle in and feel safe.
If yours look washed out the first week, do not panic. Once they are in a real school and not stressed, the color and confidence usually show up fast.
Setting up their tank
Think of these as active, midwater tetras that appreciate space and clean water more than fancy aquascaping. A longer tank beats a tall one. I have had the best luck giving them room to cruise, plus some cover so they can switch between "out in the open" and "I want a break".
- Tank size: 20 gallon long is workable for a small group, but 29-40 gallon feels a lot nicer once you have 10-12 fish
- Group size: keep at least 8, and 10-15 is where they really calm down and start acting natural
- Filtration: steady filtration with gentle-to-moderate flow; they handle current fine but do not love being blasted
- Decor: plants around the edges, open middle, a few pieces of wood or leaf litter for a more "river" feel
- Lighting: moderate; they color up well with floating plants or shaded areas
Water-wise, they are not as fussy as some wild-caught fish, but they do better if you stay consistent. Slightly acidic to neutral is a safe place to land, and warm tropical temps. The biggest thing is keeping the water clean because they are constant movers and eat like it.
Give them a dark substrate if you can. It makes a bigger difference than people think - they show more color and spend less time hugging the back glass.
What to feed them
They are easy to feed once you realize they are enthusiastic eaters, not picky gourmets. Mine did best on a rotation so they got both good dry food and some "real" stuff for color and condition.
- Staple: a quality small pellet or flake that sinks slowly
- Frozen: daphnia, cyclops, brine shrimp, chopped bloodworms (not every day)
- Live (if you do it): baby brine shrimp, grindal worms, daphnia
- Extras: occasional veggie-based flake helps if you notice stringy poop or sluggish digestion
They will overeat if you let them. Feed small portions they finish in under a minute or two, and do a second tiny feeding later if you want. Overfeeding is the fastest way to wreck their water and invite disease.
How they behave and who they get along with
Peridot tetras are lively schoolers. They are not usually "mean," but they can get nippy if the group is too small or the tank is cramped. In a proper school, they spend the day cruising midwater and doing little sparring displays that look dramatic but rarely cause damage.
- Good tankmates: other peaceful tetras, hatchetfish, pencilfish, Corydoras, smaller Loricariids, peaceful dwarf cichlids
- Use caution with: long-finned fish (guppies, bettas, fancy angels) because fin-nipping can happen
- Avoid: very tiny shrimp as a clean-up crew (adults may be ok in dense cover, babies are snacks)
If you want them looking their best, give them a group big enough that the "bossy" energy stays inside the school instead of being aimed at other fish. Also, keep the aquascape from being a solid wall of plants. They like a lane to swim.
If you see chasing and nipped fins, add more peridots before you blame the species. Bumping the group from 6 to 10 often fixes the whole vibe.
Breeding tips
They are egg scatterers, and they will absolutely eat their own eggs if given the chance. Breeding is doable, just a little fiddly, which is why I call them intermediate. The trick is conditioning hard, then moving a small group or a pair into a dedicated setup where the eggs can fall out of reach.
- Breeding tank: 10-15 gallons, bare bottom or mesh/marbles, sponge filter
- Cover: clumps of fine plants (java moss) or spawning mops
- Water: slightly softer and a bit more acidic than their main tank, warm side of tropical temps
- Conditioning: heavy frozen/live foods for 1-2 weeks
- Method: move in 1 female with 1-2 males in the evening, check for eggs the next morning, then pull adults
Fry are tiny at first. Infusoria or powdered fry food gets you through the first days, then baby brine shrimp once they can take it. Keep the water extra clean, but do tiny water changes so you do not swing parameters on them.
If you do not see eggs, do not assume it failed. Sometimes they spawn at first light and the eggs are nearly invisible unless you use a flashlight and look close.
Common problems to watch for
Most issues I have seen with peridot tetras were not mysterious diseases. It was almost always stress from being under-grouped, water quality slipping, or being stuck with the wrong tankmates.
- Fin-nipping: usually from small group size, cramped tank, or not enough cover breaks
- Ich and other "new fish" stuff: they can come in stressed from shipping, so quarantine if you can
- Bloating/constipation: from heavy dry food diets or overfeeding; add frozen daphnia and cut portions
- Faded color and hiding: often too bright, too bare, or not enough fish in the school
- Rapid breathing at the surface: check ammonia/nitrite first, then temperature and oxygenation
They do not handle ammonia or nitrite at all. If you see clamped fins, hanging in corners, or gasping, test the water before you start throwing meds at the tank.
If you keep them in a real school, stay on top of weekly maintenance, and feed like you mean it (but not too much), they are a really rewarding tetra. They act like a proper little river fish once they settle in.
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