Care guide · Freshwater · fish

Pygmy cory

Gastrodermus pygmaeus

Photo: Carnat Joel · Source · CC BY 2.0Resized and compressed; no cropping or colour changes.

The pygmy cory is among the smallest armoured catfish, yet it is much more than a miniature bottom dweller. A confident group regularly swims between plants before settling on a leaf or branch. A dark longitudinal stripe marks its silver-grey body. Older books and shop labels call it Corydoras pygmaeus; its current name is Gastrodermus pygmaeus. This Brazilian fish needs a quiet, mature aquarium with gentle substrate and suitably fine food. Its small size makes food competition, boisterous neighbours and predators especially important. Do not buy a lone specimen as a cleaner: plan a group of at least ten. With targeted feeding and sheltered resting places, the fish become far more rewarding to observe than in a bare tank where they spend their time hiding.

Plan your aquarium →

At a glance

Temperature: 22–26 °C
pH: 6.4–7.4
GH: 2–8 °dGH
Aquarium length: At least 60 cm
Minimum aquarium volume: At least 54 L
Adult size: Approximately 2–3 cm
Group size: At least 10 individuals
Swimming zone: Bottom, Middle
Temperament: Peaceful
Lighting preference: Subdued lighting
Cover: Plants and sheltered areas
Staple food: Sinking tablet, small portions
Supplementary food: Live food, Frozen food, Finely crumbled dried natural food

About this species

Adults remain about 2–3 cm long, with females usually larger and fuller than males. Their barbels help locate small food particles, while bony plates protect the body. Armour does not prevent a larger fish from swallowing them. The continuous dark flank stripe distinguishes this species from Gastrodermus hastatus, which has a conspicuous tail marking.

Other dwarf cory species have different patterns and should not be mixed up. The move to Gastrodermus reflects modern catfish research rather than a new ornamental variety. Check both the label and the fish. Hollow bellies, damaged barbels or persistent isolation deserve investigation rather than an assumption that all small catfish behave this way.

Natural habitat

The species is recorded from the Madeira drainage in Brazil. Sheltered margins, small tributary waters and seasonally flooded structures bring fish into contact with roots, leaves and fine material. They also use the water above the bottom. Reproduce that useful structure with leaves at different heights and calm passages instead of an empty sand floor.

A wooded habitat is no reason to allow aquarium water to become dirty or oxygen-poor. Limit decomposing material and remove decaying leftovers. The practical aim is shelter, a gentle substrate and access to small prey, not a claim that this layout reproduces one precisely documented locality or a single pH shared by every population.

Aquarium and layout

Use at least 60 cm length and roughly 54 litres gross for a dedicated group; prefer 80 cm or more when keeping two fish groups. Some specialist guidance allows less, but this conservative choice offers more feeding places and water stability. Gross volume is not actual water volume or a combined stocking allowance. Provide fine, non-sharp sand, open feeding patches, wood and resting leaves.

Diffuse the filter outlet and protect its intake from small fish. Establish the aquarium fully before stocking. Clean patches of substrate without stripping all biofilm at once, keep the surface accessible and fit a lid.

Water conditions

Our maintenance selection is 22–26 °C, pH 6.4–7.4 and approximately 2–8 °dGH. Published hardness limits differ; these are cautious working values, not a reason to adjust the water chemically every day. No independently justified KH target is specified. Watch pH stability when buffering is low.

Ammonia and nitrite should be undetectable. Change water regularly using suitably prepared water at a matching temperature. An occasional dash to the surface can occur in corys, but repeated gasping across the group calls for an oxygen, temperature and water-quality check.

Behaviour and group size

Keep at least ten of the same species. Lone fish and tiny remnants of groups tend to be much less confident. They occupy both bottom and midwater, so even small tetras may compete with them for food. Observe actual feeding success.

Larger cichlids can swallow them; territorial bottom dwellers may monopolise resting places. Small peaceful companions require space and separate feeding areas. Plants are not deliberately destroyed. Very young shrimps may be eaten, so this is not a guaranteed shrimp-breeding combination.

Feeding

Use a complete food that breaks into tiny edible particles and reaches the fish. Place a small piece of sinking tablet deliberately; do not leave a whole tablet simply because it is labelled for bottom feeders. Check consumption and remove leftovers. Rotate suitable small live or thawed prey, such as Artemia nauplii, as supplements.

Dried Daphnia must be finely crumbled and, if needed, briefly soaked. Offer small portions at one or two daily feedings and several locations. Waste, algae and other fishes’ leftovers do not constitute a complete diet.

Breeding

Well-fed adults may deposit individual adhesive eggs on glass or plants. There is no parental care, and adults or companions can eat them. For deliberate breeding use a quiet separate setup with a sponge filter and mature water quality. Move eggs carefully or remove the adults.

The very small fry initially need microscopic food; offer larger nauplii only once they can swallow them. Keep the bottom clean through small, well-matched water changes. Sudden cold changes and preventive medication are not routine instructions in this guide.