Pygmy Corydoras Corydoras pygmaeus

Quick Stats

Tank Setup

The Pygmy Corydoras (Corydoras pygmaeus) is the only corydoras that genuinely swims midwater — and that single fact changes everything about how you keep it. A 10 gallon long (30 × 12 inches) is the realistic minimum for a school of 6–8; a standard 10 gallon works, but the long gives them more horizontal room to school. They come from slow tributaries of the Madeira River basin in Brazil, where they sift sandy substrates for micro-crustaceans and insect larvae.

Maintain water parameters within: temperature 22–26°C, pH 6.0–7.5, hardness 2–12 dGH. They tolerate a wider range than most dwarf corys and adapt to moderately hard tap water without losing condition — which is a big part of why they are the easy-care nano cory. The one thing they will not forgive is heat: above 27°C they become stressed, refuse food, and shorten their lifespan. Aim for 24–25°C, which overlaps nicely with most tetras and rasboras.

Set up the tank with smooth sand (no sharp gravel — they sift it through their gills and sharp substrate damages their barbels), driftwood, and dense planting along the back and sides. Leave open sand in the front for sifting. A sponge filter is plenty and the gentle flow suits them; avoid strong canister return flows that pin them to the far end. A layer of leaf litter (Indian almond leaves) recreates their natural habitat and grows infusoria that fry graze on.

Tank Mates

Pygmy Corydoras are peaceful, bottom-and-midwater fish that never bother other species. They are also small enough (3 cm) that anything with a mouth big enough to swallow them is a predator. That combination makes them ideal cleanup companions for nano community tanks.

Compatible tank mates include: other Pygmy Corydoras (mandatory — they school, and they school midwater unlike other corys), Ember Tetras, Chili Rasboras, Celestial Pearl Danios, Harlequin Rasboras (in a 20 gallon), Otocinclus, Nerite Snails, Mystery Snails, Cherry Shrimp, and Amano Shrimp. They also work as a bottom school under a single Betta or a pair of Apistogramma in a 20 gallon. Avoid anything that grows over 8 cm — goldfish, angelfish, most barbs, and large gouramis will eat them.

Schooling is non-negotiable. Six is the absolute minimum; eight to ten is what I aim for. Unlike other corydoras that shuffle along the bottom in a loose group, pygmies form a true midwater school — a tight ribbon that sweeps the tank looking for food, then drops to the substrate to sift sand. A group smaller than six will hide, refuse food, and slowly waste away. They also need their own species — a single pygmy cory in a school of bronze corys will not thrive.

Diet & Feeding

Pygmy Corydoras are omnivores that spend their day sifting sand for micro-crustaceans, insect larvae, and Aufwuchs. In the aquarium they accept sinking wafers, micro pellets, frozen bloodworms, frozen daphnia, frozen brine shrimp, and live blackworms. They are not fussy eaters, but they cannot compete with fast midwater fish for flake food at the surface.

Feed small amounts twice daily. Sinking wafers (I use Hikari Sinking Wafers and Omega One Shrimp & Lobster Pellets) dropped in after lights-out reach them reliably. Twice-a-week frozen bloodworms or brine shrimp conditions them for spawning and keeps the iridescent shimmer along their flanks bright. A flake-only diet works for survival but the fish lose condition over months — barbel erosion is the classic sign of poor diet and rough substrate.

They are bottom and midwater feeders, so target-feed with sinking foods rather than relying on leftovers from surface-feeding tetras. In a community tank, the tetras will eat everything at the surface before it sinks, and the pygmies will go hungry without targeted feeding. Use a piece of tubing or a turkey baster to deliver frozen food directly to the substrate where they forage. They will also pick at biofilm and detritus, which makes them a useful cleanup fish — but they will not eat algae.

Common Health Issues

Pygmy Corydoras are hardy once established, but they are scaleless-ish fish with sensitive barbels — which makes them vulnerable to two specific problems: barbel erosion from sharp substrate and bacterial infection from poor water quality. The single biggest health issue I see is eroded barbels from keeping them on rough gravel; switch to sand and the barbels regrow within a month.

Like all corydoras they are susceptible to ich when stressed by temperature swings, but they are also sensitive to many medications. Copper-based treatments and formalin-heavy medications are toxic at standard doses — dose at 50–75% of label rate or use malachite green-free alternatives specifically labelled safe for scaleless fish. Salt is also rough on corys; if you must treat with salt, use half-strength and only for a few days.

Prevention is straightforward: stable temperature (24–25°C is the sweet spot), weekly 25% water changes with dechlorinated water, smooth sand substrate, and quarantine new fish for two weeks before adding them. Pygmies typically live 3–5 years in good conditions, with the upper end coming from cooler tanks (22–24°C) and pristine water. The single best thing you can do for them is commit to sand — it is not optional for this fish.

Breeding

Pygmy Corydoras are egg-scatterers and breed readily in a mature tank — often without any intervention. Sexing is straightforward: females are rounder and noticeably wider from above, males are slimmer and smaller. Condition a group with frozen bloodworms and live blackworms for a week, then trigger a spawn with a cool (20°C) 50% water change the morning after a warm day.

Spawning happens in T-position — the female cups her pelvic fins together, releases 2–6 eggs into the basket she forms, the male fertilises them, and she carries them to a clean surface (glass, plant leaf, driftwood) and sticks them there. A group of six can produce 40–80 eggs across a morning. Adults rarely eat eggs if well-fed, but for higher fry survival move the eggs to a separate container with an air-driven sponge filter.

Eggs hatch in 3–5 days at 25°C. Feed the fry infusoria or commercially-prepared liquid fry food for the first three days, then graduate to microworms or newly-hatched baby brine shrimp. Pygmy cory fry are tiny — smaller than a grain of rice at hatch — and grow steadily, reaching 1 cm in about six weeks and joining the adult school at around three months. This is a great first egg-layer breeding project because they spawn on their own without hormone triggers.

Frequently Asked Questions