Pygmy Cory: Caring for Corydoras pygmaeus
- aquaterraobsession
- Sep 2, 2025
- 10 min read
Updated: Sep 8, 2025
Comprehensive Biotope and Aquarium Care Sheet
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This care sheet provides detailed guidance on all aspects of Pygmy Corydoras husbandry. It outlines the fish’s native biotope and water chemistry, their diet, behavior, compatible species, and best practices for aquarium setup. The aim is not only to facilitate proper care in captivity but also to promote greater appreciation for the intricate ecosystems these remarkable fish call home.
Table of Contents
Introduction
The Pygmy Corydoras (Corydoras pygmaeus), or "pygmy cory," is a diminutive South American catfish widely admired among aquarists for its endearing appearance, peaceful temperament, and active schooling behavior. Native to the slow-moving tributaries and flooded forest margins of the Rio Madeira basin and adjacent river systems, this species is uniquely adapted to microhabitats rich in leaf litter, roots, and dense aquatic vegetation. Its ecological role as a benthic forager and its tendency to form sizable shoals make Corydoras pygmaeus a fascinating subject both for naturalists and aquarium keepers.
Summary Table
Feature | Details |
Scientific Name | Corydoras pygmaeus |
Common Names | Pygmy Cory, Pygmy Catfish |
Distribution | Madeira River (Brazil), Nanay River (Peru), Aguarico River (Ecuador) |
Habitat Type | Slow-flowing tributaries, creeks, flooded forests |
Adult Size | 1.2–1.3 in (3–3.2 cm); females slightly larger |
Lifespan | 3–5 years |
Wild Water Temperature | 72–79°F (22–26°C) |
Wild pH | 6.0–7.5 (optimal 6.4–7.4, can range 6.0–8.0) |
Wild Hardness | 2–15°dH (prefer <8°dH in natural localities) |
Behavior | Peaceful, shoaling, midwater swimmer |
Diet | Omnivorous – microinvertebrates, biofilm, detritus, algae |
Minimum Tank Size | 10 US gal/40 liters (group of 8–10+ individuals) |
Substrate | Fine sand; leaf litter beneficial |
Lighting | Dim to moderate (prefers shaded or filtered light) |
Tankmates | Small, peaceful fish; small shrimp and snails |
Not Recommended | Aggressive/large fish, strong water current |
Wild Plant Associates | Floating/strand plants, marginal grasses, duckweed |
Native Habitat and Biotope
Geographic Distribution
Corydoras pygmaeus is native to the Madeira River basin in Brazil, a major southern tributary of the Amazon River. Its range also extends to tributaries of the Nanay River in Peru and the Aguarico River in Ecuador. The type locality is near the mouth of the Ji-Paraná River, close to Calama, Brazil. Within these systems, the species shows a pronounced preference for floodplain tributaries, forest creeks, shallow pools, and periodically inundated forest floors.
Biotope Features
The Rio Madeira and its tributaries are environmentally dynamic, shaped by seasonal flood cycles (wet season: December–May, dry season: June–September), which inundate vast floodplains and forested margins. The rivers exhibit a mostly white-water character: they are rich in suspended sediments and possess neutral to slightly acidic pH with elevated dissolved organic carbon during floods.
Key biotope features include:
Water Flow: Slow-moving; significant in stagnant or gently flowing forest pools and backwaters.
Substrate: Sandy or fine silt, often blanketed by a thick layer of decaying leaf litter, twigs, and plant debris.
Vegetation: Marginal grasses (e.g., Gynerium sagittatum), aquatic and emergent herbs (Echinochloa spp.), floating plants (duckweed Lemna minuta), and dense riparian woodland providing shade.
Cover: Abundant roots, sunken branches, and overhanging vegetation provide shelter from predators and strong currents.
The natural habitat is dynamic and complex, with rich biodiversity and fluctuating microhabitats across the annual flood pulse.
Native Water Parameters
The water chemistry in the native range of C. pygmaeus can be summarized as follows:
Parameter | Typical Range |
Temperature | 22–26°C (72–79°F) |
pH | 6.4–7.4 (optimal), up to 8.0 |
Hardness | 2–15°dH (soft to moderately hard) |
Conductivity | 50–146 μS/cm (mean 83.8) |
Dissolved Organic Carbon | 128–1,024 μM |
Water Clarity | Often turbid, suspended sediment (avg. 400 mg/L) |
Oxygen Levels | High; can become depleted seasonally in stagnant pools |
Seasonal pH Variation | Slightly acidic during high water, more neutral in low-water months |
The Rio Madeira is considered a white-water river, indicating moderate softness, high suspended solids, and significant organic input. Seasonal flooding influences water chemistry by introducing tannins and detritus, resulting in darker, more acidic water in forested flood seasons.
Cohabitant Species in the Wild
Ecological research and surveys in the Rio Madeira catchment and its tributaries highlight an impressive assemblage of fish, plants, and invertebrates sharing space with Pygmy Corydoras. Understanding these communities is key for accurate biotope aquascaping and holistic aquarium setups.
Native Fish Species
Confirmed and commonly co-occurring fish species in the Rio Madeira and its tributaries include:
Family/Group | Example Species | Notes |
Characidae (Tetras) | Black neon tetra (Hyphessobrycon herbertaxelrodi), Royal tetra (Inpaichthys kerri), False rummynose (Petitella georgiae), Moenkhausia spp., Hyphessobrycon spp. | Midwater shoalers; peaceful, compatible |
Cichlidae | Apistogramma spp. (dwarf cichlids), Symphysodon tarzoo (discus), Aequidens tetramerus | Dwarf cichlids suitable; large cichlids not |
Callichthyidae | Other Corydoras: C. similis, C. hephaestus, C. hastatus, etc. | Pygmy and dwarf Corys often found together |
Loricariidae | Ancistrus dolichopterus (bushymouth pleco), Otocinclus hoppei, Peckoltia vittata, Pterygoplichthys gibbiceps | Small species are compatible |
Lebiasinidae | Nannostomus digrammus, N. eques | Pencilfish; mid- to surface dwellers |
Dentistidae | Tyttocharax madeirae | Small characins; midwater |
Additional species often encountered in the Madeira basin’s streams and pools (based on fish surveys) include:
Bryconops piracolina, Creagrutus petilus, Hyphessobrycon aff. notidanos, Hyphessobrycon lucenorum, Moenkhausia parecis, Moenkhausia cambacica, Ancistrus verecundus, Tatia intermedia, Megalechis thoracata, Rhamdia quelen, Brachyhypopomus degy, Hoplias malabaricus (occasionally, but these are larger and may prey on smaller fish).
Small surface fish like hatchetfish (Carnegiella spp., Gasteropelecus spp.) and various species of rasboras and danios are also present in the wider Amazon basin, and certain species are found in the Madeira’s tributaries when water links permit seasonal migrations.
Native Aquatic Plants
The seasonally fluctuating water levels and periodic forest inundation in the Rio Madeira region give rise to a unique aquatic flora, including both permanently submerged and emergent vegetation. The following are notable:
Plant Type | Example Species / Group | Biotope Role |
Floating Plants | Duckweed (Lemna minuta), Amazon frogbit (Limnobium laevigatum) | Provide shade, micro-habitat, roots |
Emergent Marginal Grasses | Echinochloa spp., Gynerium sagittatum, Echinolaena inflexa | Dominant on riverbanks, provide cover |
Submerged Herbs | Cabomba spp., Myriophyllum spp. | Seen in some forest pools |
Moss and Algae | Riccia spp. (liverwort), various mosses | Notable biofilm contributors |
Misc. (Herb/Grass) | Bulbostylis sp., Syngonanthus sp., Eragrostis maypurensis, Paepalanthus sp., Xyris jupicai | Common in campinarana and fragments |
Note: Heavily shaded conditions in the wild limit the presence of large rosette plants, but submerged swordplants (Echinodorus spp.) and other emergent plants may root in shallows and flooded zones. In native biotope setups, floating plants and tolerant marginal grasses are preferred over dense rooted plants.
Native Aquatic Invertebrates
Surveys from the Madeira and similar Amazonian streams highlight a high diversity of aquatic invertebrates, which form a crucial part of the food chain for Pygmy Corydoras:
Group | Example Species / Notes | Biotope Role |
Crustaceans | Amphipods (Rhipidogammarus gomeranus), freshwater copepods, ostracods | Foraged by Corys; major protein source |
Insects and Larvae | Chironomid (midge) larvae, Ephemeroptera nymphs (Baetis maderensis), Trichoptera larvae (Stactobia spp.), mosquito larvae, beetle larvae (Potamonectes spp.), Odonata larvae | Primary prey items; form micro-benthos |
Gastropods and Bivalves | Neritina snails (rare in blackwater), Physella snails | Scavenging invertebrates |
Others | Aquatic mites (many endemic species) | Regulate invertebrate communities |
These invertebrate communities are extremely diverse and are central to the natural diet of juvenile and adult Corydoras.
Diet
Diet in the Wild
Pygmy Corydoras are true omnivorous microforagers, subsisting largely on small aquatic invertebrates, tiny worms, insect larvae, crustaceans, detritus, and biofilm. Their downturned mouths and sensitive barbels are highly adapted for sifting fine sand, browsing on decaying leaf litter, and probing for hidden prey within detritus. Observations and gut analyses indicate the following main dietary components:
Microcrustaceans: Daphnia (water fleas), ostracods, copepods; especially abundant among submerged and floating vegetation.
Small Insects: Mosquito larvae, chironomid larvae, small ephemeropterans.
Benthic Worms: Small nematodes, bloodworms.
Biofilm and Periphyton: Diatoms, microalgae, filamentous cyanobacteria, and bacteria associated with decaying organic material.
Detritus: Fine organic matter and decomposing plant tissue.
Occasional Plant Material: Particularly decaying leaf fragments and microalgae.
Pygmy Corydoras actively forage throughout the day, grazing across bottom and midwater zones, and their feeding intensity is strongly influenced by seasonal food abundance, flood cycles, and social behaviors.
Captive Diet Recommendations
Key feeding guidelines for Pygmy Corydoras in aquaria:
Staple Diet: High-quality, small sinking pellets or micro-wafers designed for bottom-feeding fish. Pellets should be high in animal protein but balanced with some plant material and fiber.
Live/Frozen Foods: Regular inclusion of live or frozen bloodworms, baby brine shrimp (Artemia nauplii), daphnia, grindal worms, microworms, and cyclops. These simulate natural dietary intake and promote excellent condition and spawning.
Vegetable Matter: Offer blanched spinach, zucchini, cucumber, or shelled peas weekly. Algae wafers or spirulina-based preparations supplement plant-based nutrition.
Biofilm Encouragement: In established planted tanks, allow natural biofilm development for grazing—use driftwood, large-leaved plants, and leaf litter to promote microbial growth.
Feeding Frequency: Feed small, manageable portions 1–2 times daily, ensuring all food reaches the tank bottom and is consumed within a few minutes to avoid water quality issues.
Pygmy Corydoras have very small mouths and delicate digestive systems. All food should be finely ground or bite-size; avoid large flakes or hard pellets. Overfeeding can rapidly degrade water quality and lead to health problems.
Behavior and Social Structure
Pygmy Corydoras exhibit fascinating behavioral traits that distinguish them from many congeners:
Shoaling: Highly social, displaying strong schooling behavior. Groups of 8–12 or more promote natural, confident activity. In the wild, shoals may consist of dozens to hundreds of individuals.
Midwater Foraging: Unlike most Corydoras, which are strict bottom dwellers, Pygmy Corydoras frequently venture into midwater, hovering and swimming in small synchronized groups. This behavior is more pronounced during feeding and social interactions.
Peacefulness: Completely non-aggressive; coexists harmoniously with similar-sized, gentle species. They may be intimidated by, or avoid, larger or more boisterous tankmates.
Substrate Browsing: Uses barbels to sift through sand and detritus, constantly in search of microfauna and particles.
Facultative Air Breathing: Periodically darts to the surface to gulp air, enabling survival in low oxygen conditions—a trait supported by a modified intestine which absorbs atmospheric oxygen.
Breeding Behavior: During spawning, males pursue gravid females, which deposit single fertilized eggs on plant leaves or tank walls. No parental care is provided; adults may eat eggs if not separated.
Observation: These corys thrive in a dynamic, interactive group, showing enhanced color, foraging behavior, and overall wellness when kept in sufficient numbers.
Aquarium Tank Setup
Ensuring the correct environment for Pygmy Corydoras means mimicking their natural Rio Madeira/floodplain biotope as closely as practical.
Aquarium Water Parameters
Parameter | Range (Optimal) | Notes |
Temperature | 22–26°C (72–79°F) | Stable, avoid rapid fluctuations |
pH | 6.4–7.4 (target 6.5) | Slightly acidic to neutral |
General Hardness (GH) | 2–10°dH | Soft to moderately hard |
Carbonate Hardness (KH) | 2–8°dKH | Low-moderate buffering |
TDS | <200 ppm | Moderate dissolved solids |
Ammonia/Nitrite/Nitrate | 0/0/<20 ppm | Good filtration, weekly water changes |
Oxygen | High | Gentle aeration, avoid stagnation |
Regular testing and water changes (20–30% per week) maintain optimal conditions. For breeding or delicate wild-caught specimens, use reverse osmosis (RO) water mixed to appropriate softness.
Substrate and Decor
Substrate: Fine, inert sand (e.g., pool filter sand, natural silica) protects delicate barbels during foraging. Sharp gravel can cause barbel infection and should be avoided.
Leaf Litter: Indian almond leaves, beech, or oak leaves scattered on the bottom provide shade, natural tannins, and microhabitat for invertebrates and fry. Replace decomposing leaves every few weeks to prevent water fouling.
Driftwood/Roots: Add tangled roots or driftwood to simulate fallen trees and provide cover.
Plants: Incorporate floating and marginal plants—duckweed (Lemna minuta), Amazon frogbit (Limnobium laevigatum), java moss (Taxiphyllum barbieri), and Anubias or Cryptocoryne species. Avoid excessive dense rooted stem plants; open areas are important for free swimming.
Rocks and Caves: Provide additional surfaces and hiding spots.
Background: A dark background and soft aquascaping help create a sense of security and highlight the corys’ silvery coloration.
Filtration and Maintenance
Filtration: Gentle, efficient filtration (sponge or hang-on-back filters with low flow) prevents strong currents that can stress fish. Avoid undergravel filters that may trap debris.
Aeration: Light airstone or sponge filter promotes oxygenation, especially in tanks with dense plant growth or high bioloads.
Tank Cover: The species is active and occasionally quick to jump; tight-fitting lids prevent escapes.
Cleaning: Regular substrate vacuuming and debris removal are necessary, but do not over-clean—preserve a mature biofilm community for foraging.
Lighting
Level: Soft, dim to moderate lighting is preferred; floating plants or strategic use of decor diffuse overhead light and replicate dappled floodplain shade. Too-bright lighting leads to stress and reduced activity.
Day Length: 10–12 hours daily is recommended to mimic natural cycles.
Compatible Aquarium Tankmates
Pygmy Corydoras is best suited for peaceful, nano-community setups. Avoid tankmates that are large, aggressive, or boisterous, as they may intimidate or prey on these tiny catfish.
Fish Tankmates
Highly recommended companions include:
Fish Species | Notes |
Neon tetra | Paracheirodon innesi – classic South American nano fish, peaceful, matches habitat |
Ember tetra | Hyphessobrycon amandae – small, calm, and visually striking companion |
Harlequin rasbora | Trigonostigma heteromorpha – peaceful, similarly sized |
Chili rasbora | Boraras brigittae – tiny, non-intimidating |
Guppies and Endlers | Peaceful, smaller strains preferred |
Celestial pearl danio | Danio margaritatus – nano, non-nippy |
Kuhli loach | Pangio spp. – bottom-dwelling but gentle |
Otocinclus catfish | Peaceful, ideal algae eaters |
Pencilfish | Nannostomus spp. – small surface dwellers |
Apistogramma dwarf cichlids | Only smallest, peaceful species |
Other small Corydoras | C. hastatus, C. habrosus – compatible group shoalers |
A school of their own species remains important; groups of other peaceful shoaling fish add activity without stress.
Invertebrates
Shrimp: Cherry shrimp (Neocaridina davidi), Amano shrimp (Caridina multidentata)—adults generally safe, but tiny shrimp fry may be consumed.
Snails: Nerite, mystery, and ramshorn snails pose no threat and help clean the tank.
Other: Avoid crayfish or aggressive, predatory invertebrates.
Aquatic Plant Selection
Plants serve dual roles—providing microhabitat and improving water quality. Best suited species for Pygmy Corydoras setups include:
Plant Type | Species | Notes |
Floating Plants | Duckweed (Lemna minuta), Amazon frogbit (Limnobium laevigatum) | Softens light, offers cover |
Low-Growing Mosses | Java moss (Taxiphyllum barbieri), Christmas moss | Preferred spawning sites; natural shelter |
Anubias | Anubias nana, A. barteri | Hardy, tolerant of low light, broad leaves |
Cryptocoryne | Cryptocoryne wendtii and relatives | Slow growing, attractive colors |
Vallisneria | V. spiralis | Ribbon-like leaves mimic wild habitat |
Amazon Sword | Echinodorus amazonicus | Classic Amazonian—use sparingly in small tanks |
Marimo moss balls | Aegagropila linnaei | Nibble surface, water polisher |
Wild biotopes may feature more marginal grasses and floating vegetation than rooted stems. In tanks, emulate this with dense planting in background and sides, leaving open swimming space central and front.
References to Native Cohabitant Species
Category | Representative Species / Groups | Notes/documentation |
Fish | Apistogramma spp., Moenkhausia parecis, Hyphessobrycon spp., Petitella georgiae, Nannostomus spp., Otocinclus hoppei, Inpaichthys kerri | Surveyed in Madeira basin rivers and tributaries |
Plant | Duckweed (Lemna minuta), Gynerium sagittatum, Echinochloa spp., Cabomba spp., Myriophyllum spp. | Documented on riverbanks, flooding margins, varzea |
Invertebrate | Aquatic mites (various, many endemic), copepods, ostracods, amphipods (Rhipidogammarus), chironomid larvae, snails (Neritina spp.) | Multiple biological records for Madeira basin and analogs |
Conclusion
The Pygmy Corydoras is a remarkable example of Amazonian biodiversity adapted to dynamic, flood-prone environments. Successful care in captivity is grounded in an understanding of its natural Rio Madeira biotope and social habits.
Key principles include providing a soft, sandy substrate for substrate foraging; fostering a well-oxygenated, gently filtered, and softly lit tank; offering abundant shelter from driftwood, roots, and floating plants; and maintaining a diverse, protein-rich diet with live/frozen components.
Above all, Pygmy Corydoras thrive in groups, both for their well-being and for the enjoyment of aquarists seeking to observe their interactive and charming behaviors.
Replicating the natural habitat through informed aquascaping, careful species selection, and water chemistry management is the best way to ensure these diminutive catfish remain healthy, display their full range of behaviors, and, perhaps, even breed in the home aquarium. By following these guidelines, aquarists foster a slice of Rio Madeira’s living legacy—a vibrant, thriving, and ecologically nuanced aquarium community.
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