How big do pygmy corys get?
Pygmy corydoras (Corydoras pygmaeus) are among the smallest corydoras. Adults are typically around 1 inch (about 2.5 cm), and sources commonly give a range of about 0.75 to 1.3 inches (roughly 2 to 3 cm). Females tend to be slightly longer and rounder than males. Juveniles are sold even smaller, often around half an inch.
They also behave a little differently from the larger corys. Rather than staying glued to the substrate, pygmy corys often swim in the lower and middle parts of the water, which makes them easy to watch in a nano tank.
Pygmy cory vs. other corydoras sizes
Corydoras vary a lot in size, which changes how many fit into a tank. Approximate adult sizes cited by hobby sources include:
| Species | Approximate adult size |
|---|---|
| Pygmy cory | About 1 inch |
| Panda cory | About 2 inches |
| Bronze or albino cory (C. aeneus) | Up to roughly 2.5 to 2.75 inches |
| Peppered cory | About 2.5 inches |
Species also look similar. The dwarf Corydoras habrosus has a horizontal stripe like the pygmy but is often described as slightly larger and more spotted, so check what you are buying.
How big of a tank do corydoras need?
There is no single number for every cory. As a rough guide, small species suit smaller tanks, while larger corys do better with more floor space. Hobby sources commonly suggest:
- Pygmy corys: about 5 to 10 gallons for a small school, with 10 gallons or more usually advised.
- Panda corys: roughly 10 to 20 gallons.
- Peppered and other larger corys: at least 10 gallons, with more being better for a good-sized group.
More important than the exact volume is giving the group enough room and staying within the stocking guidance for your filtration and maintenance routine. Consider the cory’s adult size and group size together.
How many pygmy corys in a 10 gallon?
Groups of at least six are generally recommended, and many keepers prefer eight to ten or more because pygmy corys are tiny, social, and look best in a large shoal. In a 10 gallon, a group of roughly 6 to 10 pygmy corys is a common starting point, if the tank is well filtered, well planted, and stocked lightly with other fish.
If you want other fish too, remember that the corys are not the only load on the tank. Keep the combined fish count modest and prioritize a species-only or mostly corys group if you want to see their natural behavior.
How many corys in a 20 gallon?
The answer depends on the species:
- Pygmy corys: a 20 gallon can host a bigger school of them, and some keepers go to a dozen or more. These fish are so small that the limiting factor is often stability of the water and tankmates rather than space.
- Larger corys such as panda or bronze: commonly a group of six in a 20 gallon, with possibly a few more in a long tank.
Do not mix several species of cory in a small group each. Corys generally prefer to shoal with their own kind, and a group of six or more of one species is better than two of each of three.
Sand or gravel?
Corydoras forage with sensitive barbels, so soft substrates are the safer choice. Sand is usually considered ideal, and very fine, smooth gravel can also work. Sharp or coarse gravel may wear down or injure their barbels over time, which can lead to infections.
Keep the substrate clean, since waste that sits in sand or gravel can affect them directly. Because they eat from the bottom, feed sinking foods such as sinking wafers, pellets, or frozen foods like bloodworms.
Tankmates and feeding in a small tank
Pygmy corys do well with other peaceful nano fish, such as the spike-tailed paradise fish, and small invertebrates, but keep tankmates calm and small. Avoid anything large enough to eat them, and avoid boisterous bottom dwellers. For example, loaches like the zebra loach can compete for space and are better kept apart from tiny corys.
Plants and cover help the group feel secure. If you keep them in a planted, species-only tank, some keepers report that they breed as a colony, but breeding is never guaranteed.
Pygmy cory vs. habrosus
Both species are tiny and have a horizontal line, so they are frequently confused in shops. Pygmy corys are the smaller of the two, and habrosus usually shows additional spots. Both are suited to nano setups and have similar needs, but avoid mixing species if you want a tight, natural-looking school.
Related reading
If you are exploring other bottom-dwellers, see the black kuhli loach tank size guide for a quiet, nocturnal alternative, or our overview of the best bottom-dwelling freshwater fish.