Pygmy Corydoras Care Guide: Tank Size, Diet & Tank Mates

Species Overview#

Pygmy corydoras (Corydoras pygmaeus) are the smallest commonly kept member of the corydoras genus and one of the few catfish that genuinely belong in a nano tank. Adults top out around 1.2 inches (3 cm), they school in tight, coordinated groups, and unlike almost every other cory you'll see at a local fish store, they spend most of their day in the middle of the water column rather than rooting around the substrate. A school of 10 darting in unison through a planted 10-gallon is one of the more underrated sights in the freshwater hobby.

They come from the Rio Madeira basin in Brazil — soft, slightly acidic blackwater streams choked with submerged roots, leaf litter, and fine sand. They're hardy enough for a beginner who has cycled a tank properly, but their tiny size leaves zero margin for ammonia spikes or coarse gravel that shreds their barbels. Get the substrate, school size, and tank shape right, and you'll have a peaceful nano centerpiece for 3 to 5 years.

Adult size

1.0-1.2 in (2.5-3 cm)

Lifespan

3-5 years

Min tank

10 gallons (long) for school of 8+

Temperament

Peaceful, schooling

Difficulty

Beginner with stable parameters

Diet

Omnivore, mid-water feeder

Natural Habitat#

Corydoras pygmaeus lives in the slow-moving tributaries and flooded forest margins of the Rio Madeira drainage in Brazil. The water there is soft and acidic, stained by tannins leaching from decaying leaves and submerged wood, and the substrate is fine sand or silt rather than the gravel you find in temperate rivers. Current is minimal — these are backwater fish, not stream specialists — and overhead vegetation keeps the light dim and dappled.

In the wild they form loose mid-water schools of dozens to hundreds, often shoaling alongside small tetras and other nano species. The mid-water habit is a defense response to predators that hunt the substrate, and it's the single trait that most distinguishes them from larger cory species. Replicating this environment in the aquarium — soft water, fine sand, dense planting, gentle flow — pays off in both behavior and longevity.

Appearance & Size#

Pygmy corydoras have a slim, elongated body with a metallic silver base color and a sharp black horizontal stripe running from the gill plate to the base of the tail. A second, shorter black bar sits at the caudal peduncle, and the belly is pale white. Both sexes look similar, but mature females are noticeably wider and rounder when viewed from above, especially when carrying eggs.

They are routinely confused at the local fish store with two close relatives — Corydoras hastatus and Corydoras habrosus — and many shipments arrive mislabeled. C. hastatus (dwarf cory) is similar in size and also schools mid-water, but it has a single black blotch at the tail base rather than a continuous lateral stripe. C. habrosus (salt and pepper cory) is shorter and stockier, marked with a broken pattern of black blotches and spots rather than a clean horizontal stripe, and it stays on the substrate like a normal cory. If you specifically want the mid-water schooling behavior described in this guide, you want pygmaeus — verify the lateral stripe before you pay.

Lifespan#

Pygmy corydoras typically live 3 to 5 years in a well-maintained aquarium. That's shorter than larger cory species (which often hit 8 to 10 years) but normal for a fish this small. Lifespan is tied directly to water quality and stocking — schools of 8 or more in a stable, soft-water tank consistently outlive isolated fish or fish kept in groups of 3 or 4, where chronic stress shortens their lives even when water parameters look fine on paper.

Most early losses come from one of three causes: an uncycled tank at stocking, coarse gravel that erodes their barbels and opens the door to bacterial infection, or shipping stress on wild-caught individuals that never fully acclimate. Captive-bred stock from a reputable supplier is more forgiving and worth seeking out.

Water Parameters & Tank Requirements#

Get the chemistry and tank shape right before the fish arrive. Pygmy corydoras are not fragile, but their tiny body mass means they have almost no buffer against ammonia spikes, sudden temperature swings, or the slow grind of a pH that drifts a full point between water changes.

Ideal Water Parameters#

Aim for a temperature of 72 to 79°F (22 to 26°C). They tolerate a wider range than that, but the upper end of the natural range stresses them and shortens their already-short lifespan. Keep pH between 6.0 and 7.5 — they originate from blackwater habitats below pH 6.5, but tank-bred specimens adapt fine to neutral water as long as it's stable.

Hardness is more flexible than many sources suggest. Anything from 2 to 12 dGH works, with the soft end better for breeding and the upper range still well-tolerated for general keeping. Ammonia and nitrite must read zero, full stop. Nitrate should stay under 20 ppm — a weekly 25% water change in a moderately stocked tank usually keeps you in that range without issue.

Minimum Tank Size & Footprint#

A 10-gallon long is the practical minimum for a school of 8 to 10 pygmy corydoras. Tank shape matters more than raw volume — these fish swim laterally in coordinated groups, so a long, shallow footprint (the standard 20" x 10" x 12" of a 10-gallon long) gives them more usable space than a tall 10-gallon column. A 20-gallon long is the sweet spot if you want to keep a school of 15+ alongside small tetras or rasboras.

Substrate is non-negotiable. Use fine sand (pool filter sand, Caribsea Super Naturals, or aquarium-specific play sand) rather than gravel of any size. Pygmy corydoras sift sand through their gills as part of normal foraging behavior, and gravel — even smooth aquarium gravel — abrades and eventually erodes the delicate sensory barbels around their mouths. Once damaged, barbels rarely recover and the underlying tissue is prone to bacterial infection.

Filtration & Flow#

A standard sponge filter driven by a quiet air pump is the ideal filter for a pygmy cory tank. It provides biological filtration, surface agitation for oxygen exchange, and gentle flow that won't push 1-inch fish across the tank. A small hang-on-back filter works too — just baffle the output with a piece of filter sponge or a spray bar to break up the current.

Avoid powerheads, strong canister returns, or anything that creates a noticeable current. These are slow-water fish, and high flow keeps them pinned to the corners or hiding in plants instead of schooling in the open. If you can see the plants swaying constantly, the flow is too strong.

Planting & Décor#

Dense planting transforms a pygmy cory tank. Java fern, Anubias, hornwort, and floating plants like frogbit or Amazon frogbit provide the dim, shaded environment they evolved in and give them safe corridors to school through. Driftwood and a thin layer of Indian almond leaves or oak leaves on the substrate replicate the blackwater feel and release tannins that gently lower pH.

Lighting should be moderate to dim. Bright, open tanks stress them and bleach their color. If you're running high-PAR lighting for plants, use floating cover or tall background plants to create shaded zones the school can retreat into.

Diet & Feeding#

Pygmy corydoras are omnivores with a strong preference for small live and frozen foods. Their tiny mouths and mid-water feeding habit make them genuinely different from larger cories — you cannot just drop a sinking pellet in front of them and walk away.

What Pygmy Corydoras Eat#

In the wild they pick zooplankton, microcrustaceans, insect larvae, and small invertebrates from the water column and from leaf litter. In the aquarium they accept a wide range of prepared foods as long as the particle size is right. Sinking micro pellets (Hikari Micro Wafers, Bug Bites Micro Granules, Repashy Bottom Scratcher) form a solid daily staple. Crushed flake works for variety. Repashy gel foods give them something to graze on for several hours after feeding.

Feeding Tips#

Feed once or twice a day, only what the school will consume in 2 to 3 minutes. Because they feed mid-water as much as on the substrate, choose foods that sink slowly — many micro pellets are designed exactly for this. Frozen baby brine shrimp, daphnia, micro worms, and cyclops are excellent supplements 2 to 3 times a week and trigger noticeably more active foraging behavior.

For a more thorough overview of small-fish feeding strategy, see our freshwater fish guide.

Tank Mates & Compatibility#

Pygmy corydoras are completely peaceful and will not bother any other fish. The compatibility question runs the other direction — what won't bother them, eat them, or outcompete them at feeding time.

Best Tank Mates#

Stick with small, peaceful species that share their preference for soft, slow-moving water. Ember tetras, neon tetras, chili rasboras, exclamation point rasboras, harlequin rasboras, and small livebearers like endlers all coexist beautifully. Other small Corydoras species (panda, julii, and habrosus) school together with pygmies in larger tanks, though they tend to form separate sub-groups by species rather than mixing fully.

Adult dwarf shrimp — cherry, amano, ghost — are safe with pygmy corydoras. Shrimplets and very young juveniles may be picked off, but a heavily planted tank gives them enough refuge that a stable shrimp colony usually establishes itself alongside the cory school.

Species to Avoid#

Avoid any fish over about 2 inches that might intimidate, outcompete, or predate on a 1-inch cory. That rules out angelfish, larger gouramis, most cichlids, and any of the larger barbs (tiger barbs are notorious fin-nippers and will harass anything smaller than themselves). Bettas are a coin flip — some individuals ignore pygmy corydoras entirely, others target them as snacks.

Goldfish, oscars, severums, and any large-bodied predator are obvious nos. Less obvious: avoid keeping pygmy corydoras with significantly larger Corydoras species, like C. aeneus (bronze) or C. paleatus (peppered). The big cories will hoover up sinking food before the pygmies get to it, leading to slow starvation.

Keeping Them in Schools#

Six is the absolute floor — 10 or more is what you actually want. Pygmy corydoras kept in groups smaller than 6 hide constantly, lose color, refuse to school, and die early. The mid-water schooling behavior that makes this species worth keeping in the first place only emerges in larger groups.

Breeding Pygmy Corydoras#

Pygmy corydoras breed readily in the aquarium once they're well-conditioned and the school is stable. They use the same T-position spawning behavior as larger corydoras species, but everything happens at miniature scale.

Sexing & Conditioning#

Sexing is straightforward in mature fish. Females are noticeably wider and rounder when viewed from directly above, especially when gravid — the body widens past the dorsal fin in a clear teardrop shape. Males stay slim and torpedo-shaped. Below about 9 months of age, sexing by appearance alone is unreliable.

Condition the school for 1 to 2 weeks on heavy live and frozen foods — baby brine shrimp, daphnia, and micro worms work well. Keep up daily feedings and maintain pristine water quality with twice-weekly small water changes.

Spawning & Egg Care#

Trigger spawning with a 30 to 40% water change using cooler, soft water — a 5°F drop is typical, mimicking the seasonal rainfall that triggers wild breeding. Within a day or two, males will begin chasing females and the classic T-position spawning embrace will follow. Females deposit small clutches of 1 to 4 sticky eggs at a time on plant leaves, glass, or filter intakes, returning multiple times until 30 to 100 eggs are laid.

Adults will eat eggs and fry, so either remove the parents or remove the eggs to a small bare-bottom hatching tank with matched water and gentle aeration. Eggs hatch in 3 to 4 days at 75°F. Fry are tiny — feed infusoria or vinegar eels for the first week, then move to baby brine shrimp.

Common Health Issues#

Pygmy corydoras are hardy when their basic needs are met, but their small size makes them vulnerable to a few specific problems.

Barbel Erosion#

The most common preventable issue. Barbels — the sensory whiskers around the mouth — wear down or rot off entirely when the substrate is too coarse, when water quality slips, or both. Once damage starts, secondary bacterial infection often follows and the fish stops feeding effectively because it can't sense food on the substrate.

Prevention is simple: fine sand substrate from day one, and weekly water changes that keep nitrates under 20 ppm. Treatment for already-damaged barbels means moving the fish to clean, soft water with sand substrate and treating any visible bacterial infection with a cory-safe antibiotic like kanamycin. Barbels regrow slowly if the damage is mild and water quality stays high.

Ich & Skin Flukes#

Pygmy corydoras catch ich (white spot disease) easily, especially after the stress of shipping or a temperature crash. Standard ich treatment works, but corydoras as a group are sensitive to copper and many ich medications — dose at half-strength and watch the fish closely for signs of distress (gasping, lying on the substrate). Raising temperature gradually to 82°F for the duration of treatment speeds the parasite's life cycle and shortens the outbreak.

Skin flukes occasionally show up on new arrivals and present as flashing (rubbing on substrate) and excess mucus production. Praziquantel-based treatments are the standard fix and are well-tolerated by pygmy corydoras at label dose. Quarantine new fish for 2 to 4 weeks before adding them to your display tank to catch both issues before they spread.

Where to Buy & What to Look For#

Where you source pygmy corydoras matters more than the price you pay. A healthy, properly identified school from a knowledgeable shop will outlive a cheap, mislabeled batch from a chain store every time.

Finding Healthy Specimens at Your Local Fish Store#

Look for fish that are actively schooling mid-water rather than hiding in corners or sitting motionless on the substrate. Bellies should be rounded and full — sunken or pinched abdomens indicate starvation or internal parasites and the fish rarely recover. Barbels should be intact and visible around the mouth; absent or shortened barbels are a hard pass.

Check coloration. The lateral stripe should be sharp black against a clean silver base. Faded color, pale gills, or visible white spots are all reasons to walk away. Watch the school feed if the staff will let you — fish that ignore food at the store will usually keep ignoring it at home.

Price & Availability#

Expect to pay $3 to $6 per fish at most local fish stores, with bulk pricing if you buy 10 or more. Captive-bred stock is the standard for this species and is what you want — wild-caught pygmy corydoras occasionally show up but carry higher parasite loads and shipping mortality. Reputable shops will tell you the source on request.

Availability is generally good year-round, though specific shipments can be hit-or-miss at smaller stores. Call ahead and ask if they have Corydoras pygmaeus in stock and confirm they're not selling you C. hastatus or C. habrosus by mistake.

Acclimation#

Drip acclimate over 60 to 90 minutes — pygmy corydoras don't tolerate sudden parameter changes well. For full method, see our acclimation guide. Add the entire school at once rather than splitting introductions; latecomers often struggle to integrate into an already-established group.

If you're planning a 10-gallon long for a school of 8 to 10, our 10 and 20-gallon tank guide covers stocking math, filtration sizing, and aquascape patterns that work well for nano cory species. For other small schooling cories worth considering alongside or instead of pygmaeus, see panda corydoras, albino corydoras, and bronze corydoras.

Quick Reference#

• Tank size: 10 gallons (long) minimum for a school of 8-10; 20-gallon long for schools of 15+
• Temperature: 72-79°F (22-26°C)
• pH: 6.0-7.5 (stable matters more than exact value)
• Hardness: 2-12 dGH
• Substrate: Fine sand only — gravel causes barbel erosion
• Flow: Low; sponge filter or baffled HOB
• School size: 6 minimum, 10+ recommended
• Diet: Omnivore, mid-water feeder — micro pellets, frozen baby brine, daphnia, micro worms
• Tankmates: Small tetras, rasboras, dwarf shrimp, peaceful nano species
• Avoid: Anything over 2 inches, large cories that outcompete at feeding, fin-nippers, cichlids
• Lifespan: 3-5 years
• Difficulty: Beginner with stable parameters and proper substrate