Wavy cory (Corydoras undulatus) care guide

Group
Freshwater fish
Other names
Undulatus cory, Wavy catfish, Gastrodermus undulatus, Corydoras undulatus
Family
Callichthyidae (armoured catfishes)
Origin
South America: the lower Paraná basin and coastal rivers of southern Brazil, with Argentina (type locality La Plata, Buenos Aires).
Water
freshwater
Maximum size
4.4 cm
Temperature
22–26°C
pH
6–8
Hardness
Soft to moderately hard (2–25 dGH)
Minimum tank
60 litres
Care level
beginner
Temperament
peaceful

Care

A small, peaceful shoaling Corydoras for a group of six or more. About 60 litres is enough for a group (our estimate from adult size). Use soft sand, or at least smooth rounded gravel: sharp or chipped gravel wears down the barbels, which then become infected. Add driftwood, plants and some shade from overhanging wood, rockwork, tall or floating plants, while leaving open sand for foraging. Keep current gentle and the water well oxygenated, and do regular partial water changes, as Corydoras are sensitive to nitrate and dirty substrate. PlanetCatfish gives no water figures. Wikipedia gives 22–26 °C, pH 6.0–8.0 and 2–25 dGH, but notes these values are unverified; coming from the southern Paraná region it should also cope with slightly cooler water. Identification and sexing: named for its wavy (undulating) dark pattern over a pale body. PlanetCatfish gives a maximum of 4.4 cm SL. Females grow larger and are noticeably broader and fuller-bodied when seen from above; mature males are slimmer and have more pointed tips to the paired fins. Name: now classified as Gastrodermus undulatus after the 2024 split of Corydoras; still sold as Corydoras undulatus. Status: IUCN Least Concern (per Wikipedia; PlanetCatfish lists it as not evaluated). Sources: PlanetCatfish (planetcatfish.com/common/species.php?speciesid=509); Wikipedia (en.wikipedia.org/wiki/Gastrodermusundulatus). Checked October 2026.

Diet

An omnivorous scavenger that sifts the sand for small invertebrates. Offer good-quality sinking pellets, tablets or granules as the staple, plus frozen or live bloodworm, Daphnia, brine shrimp and small worms several times a week (bloodworm, white worm, grindal worm, Daphnia). Make sure food actually reaches the bottom, as faster mid-water fish will take it first, and feed some after lights-out.

Breeding

PlanetCatfish holds a single breeding report. Wikipedia notes spawning among dense plants with no parental care. Condition a group on live and frozen foods, then trigger spawning with a large, slightly cooler water change; eggs are stuck to plants and glass. Remove the eggs (or the adults) and raise the fry on microworm and baby brine shrimp in very clean water.

Compatibility and tank mates

A peaceful shoaling catfish for a calm community of similar-sized fish: small tetras, pencilfish, hatchetfish, rasboras, dwarf cichlids such as Apistogramma, and other Corydoras or small plecos. It suits most calm community tanks. Avoid large or boisterous cichlids, fin-nippers that pester bottom-dwellers, and any fish big enough to swallow it. Very small shrimp fry may be eaten, but adult shrimp and snails are left alone.

Last updated 5 October 2026. Community-edited care guide on Aquatic-Auctions.

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