Pasca
Paragoniates alburnus
The Pasca features a slender body with a silver hue, a pointed snout, and a pronounced dorsal fin, displaying iridescent blue reflections.
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About the Pasca
Paragoniates alburnus (often called the pasca) is a slim, silvery Amazon characin that tops out around 6-7 cm. Its vibe is very much "open-water, always on the move," so it does best in a roomy tank with a current and a group of its own kind.
Also known as
Quick Facts
Size
6.7 cm SL
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
53 gallons
Lifespan
5 years
Origin
South America
Diet
Omnivore leaning carnivore - small insects/larvae, crustaceans, frozen foods, quality pellets
Water Parameters
23-27°C
5.6-7.8
3-10 dGH
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Calculate heater sizeCare Notes
- Give them a long tank with real swimming room (4 ft+ is worth it) and a tight lid - they spook and jump hard.
- Keep in a group; sources suggest at least 4–5 individuals, and provide a large tank volume recommendation.
- Keep the water soft to moderately soft and slightly acidic: pH ~5.5–7.0 and low-to-moderate hardness (about 3–10 dGH).
- Temp in the mid 70s F is a safe zone (around 74-78F); if you push it hot, crank aeration or you will see them hugging the surface.
- Feed like a micro-predator: small floating foods and meaty stuff (daphnia, brine shrimp, chopped bloodworms) in small hits 2-3 times a day so the shy ones actually get some.
- Tankmates: think fast, non-bitey fish that like similar water (other midwater characins, peaceful bottom fish like Corydoras); avoid slow fancy fins and anything tiny enough to be viewed as food.
- Watch for stress signs: faded color, clamped fins, glass surfing, and sudden jumpiness usually means water is off or the tank is too bright and bare - add floating plants and dim the lights.
Compatibility
Good Tankmates
- Fast, midwater schooling tetras that can handle a little attitude - think Buenos Aires tetras or larger rummynose groups. They stay out of the Pasca's face and the school keeps anyone from getting singled out.
- Bigger, sturdy rasboras or danios (giant danios are a classic) - quick enough that the Pasca's bluff-chasing does not turn into actual damage.
- Peaceful bottom crews that mind their business - Corydoras in a proper group, or a bristlenose pleco. Pasca mostly cruises midwater, so this combo usually stays drama-free.
- Medium, calm cichlids that are not fin-picky and have some size - like keyholes or a mellow acara in a roomy tank. They can hold their space without turning it into a brawl.
- Other robust characins around the same size (not tiny stuff) - silver dollars or similar 'big, chill' schooling types, assuming you have the swimming room.
Avoid
- Hard-water livebearers (typical mollies/platies) if you are keeping Pasca in its preferred soft, acidic water.
- Small, bite-sized community fish - neon tetras, ember tetras, guppies, small rasboras. Pasca can be a little predatory and the tiny guys get stressed or disappear.
- Slow fish with fancy fins - bettas, fancy guppies, longfin angels. Even if Pasca is not trying to be a jerk, the fins look like targets and the slow pace invites bullying.
- Nippy or aggressive tankmates that escalate things - tiger barbs, serpae tetras in small groups, or hyper cichlids. Pasca will not back down and it turns into nonstop chasing.
Where they come from
Pasca (Paragoniates alburnus) is one of those South American characins that looks like it should be easy because its a "tetra-shaped" fish, then it humbles you. Theyre river fish from fast, open water systems in the Amazon and Orinoco basins, usually cruising midwater where theres current, oxygen, and space.
Think "built for swimming" more than "built for a planted nano." If you set them up like a generic community tetra, they tend to get skinny, spooked, and short-lived.
Setting up their tank
Give them room first, decoration second. They want length to cruise, not a tall box full of hardscape. A bigger footprint also makes them way less twitchy.
- Tank size: I would not bother under 4 ft length. Bigger is noticeably easier.
- Group size: keep a real group (8-12+). Small groups stay nervous and beat up weaker fish.
- Flow and oxygen: strong filtration, steady current, and lots of surface agitation.
- Cover: open swimming lane in the middle, plants and wood pushed to the sides/back for security.
- Lighting: moderate is fine. Too bright and bare can make them skittish.
They are jumpers. A tight lid is not optional, especially the first few weeks and anytime you spook them doing maintenance.
Water wise, they do best in clean, soft-ish water with a bit of acidity, but stability matters more than chasing a perfect number. What they do not forgive is stale water and low oxygen. If your tank ever smells "fishy" between water changes, theyre going to be the first to complain.
- Temperature: mid 70s to low 80s F (24-28 C) depending on your stock list
- pH: roughly 6.0-7.2 is a comfortable zone for most setups
- Hardness: softer to moderate
- Maintenance: frequent water changes and good mechanical filtration (they like clean water, and they eat a lot)
If you can, add a powerhead or directional return to create a steady "river lane" across the front of the tank. Theyll use it constantly, and it keeps them from pacing the glass.
What to feed them
Pasca are active midwater predators/foragers. In practice, that means they need more than flakes and the occasional frozen cube. The big mistake I see is underfeeding or feeding only dry food, then wondering why the fish look narrow behind the head.
- Staples: quality small pellets (they take them better if you pre-soak for a few seconds)
- Frozen: mysis, brine shrimp, daphnia, chopped krill, bloodworms in moderation
- Live (great for conditioning): blackworms, live daphnia, baby guppies only if youre comfortable with that route
- Extras: insect-based foods (small bug pellets, freeze-dried black soldier fly larvae crushed up)
Feed smaller amounts more often. Two to three small feedings a day keeps their weight on and cuts down on frantic feeding aggression.
Watch them eat. Healthy Pasca eat with confidence and stay sleek but not bony. If a couple fish always hang back, thats usually social stress or not enough food getting to them. Spread food across the tank so the bold ones dont hog everything.
How they behave and who they get along with
In a proper group they look amazing: tight midwater schooling, quick turns, and lots of "testing the current." In a too-small tank or too-small group, they get jumpy and may start nipping or chasing.
- Best tankmates: other robust, similarly sized South American fish that like flow (larger tetras, some peaceful characins, medium cichlids that are not fin-nippers), sturdy catfish
- Avoid: slow long-finned fish (angels, bettas, fancy gouramis), tiny tetras, tiny rasboras, and anything that stresses easily
- Bottom crew: Corydoras can work in calmer zones, but pick bigger species and give them slack water areas
They are not "aggressive" like a piranha, but they are fast, competitive feeders. If you keep timid fish with them, the timid fish usually lose out at dinner.
If you see constant sparring inside the group, its usually a space/flow/cover issue. More length, a stronger current lane, and more fish (yes, more) often calms the whole dynamic.
Breeding tips
Breeding Pasca in the average home aquarium is possible but not common. Theyre egg scatterers, and the adults are not going to politely ignore their own eggs. Most people who succeed treat it like breeding bigger tetras: conditioning, then separating adults from eggs.
- Conditioning: heavy live/frozen feeding for a couple weeks and lots of clean water changes
- Spawning tank: separate tank with dim light, gentle flow, and either a spawning mop or marbles/mesh so eggs fall out of reach
- Trigger: a large cooler water change (simulating rain) can help, but dont swing parameters wildly
- After spawning: remove adults quickly, then add gentle aeration and keep water very clean
If you try to raise fry, plan on tiny foods immediately (infusoria, rotifers, or commercial liquid fry foods), then transition to baby brine shrimp. Missing that early window is the usual reason fry disappear.
Common problems to watch for
Most issues with Pasca trace back to three things: not enough space, not enough oxygen, or not enough food. Theyre the kind of fish that look "fine" for a month, then crash if the setup is off.
- Skinny fish or pinched bellies: underfeeding, too much competition at meals, or internal parasites (especially in new imports)
- Glass surfing and spooking: tank too small, group too small, too bright/bare, or sudden activity outside the tank
- Fin nipping: usually stress plus cramped quarters, sometimes a sign the group is too small
- Gasping or hanging near the surface: low oxygen, dirty filter, not enough surface agitation
- Ich and other spot issues after purchase: stress from shipping plus weak immune response
Dont skip quarantine. Wild-caught or stressed shipments can come in with parasites. If you add them straight to a display, youll be trying to treat a big, fast, oxygen-hungry schooling fish in the main tank, which is never fun.
If you want one simple "health check" habit: watch their body shape weekly. Once they start losing weight, you have a short window to fix it. Bump feeding frequency, spread food out, and double check flow and filtration before you reach for meds.
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