Peridot tetra

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.

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.

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

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.

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.

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

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.