Pygmy corydoras

1) Where they come from

Pygmy corydoras (Corydoras pygmaeus) come from small, slow-moving waters in South America—think quiet creeks and backwaters with leaf litter, roots, and soft sand. That background explains a lot: they’re built for sifting the bottom, they like cover, and they’re way happier in groups than alone.

2) Setting up their tank

These guys are tiny, but don’t treat them like decorations for a nano tank with zero stability. A 10 gallon works great for a proper group, and a 15–20 gallon is even nicer if you want them to really show their personality.

• Tank size: 10+ gallons for a group (bigger is easier to keep stable)
• Group size: 8–12 is the sweet spot; 6 is the bare minimum in my experience
• Temp: mid-70s°F (around 23–25°C) keeps them active and comfortable
• pH/hardness: they’re flexible if you keep it steady; slightly acidic to neutral is typical
• Flow: gentle to moderate—enough to keep water fresh, not enough to pin them down

Substrate matters more than most people think. They spend their day nosing around, and rough gravel will slowly beat up their barbels. Fine sand is the easiest win you can give them.

Plants and cover make them bolder. Mine always came out more when I gave them clumps of moss, crypts, and a few little caves or root tangles. They’ll also use midwater space a lot more than larger cories, especially if they feel safe.

• Lighting: moderate; floaters help if your tank is bright
• Decor: leaf litter (catappa/oak) looks natural and they love poking around it
• Filtration: sponge filters are perfect; gentle, safe intake, lots of biofiltration
• Maintenance: small weekly water changes beat big “once in a while” changes

3) What to feed them

Pygmy cories are not “cleanup crew.” They’ll eat leftovers, sure, but you should feed them like a real fish you care about. They have small mouths, and faster tankmates will absolutely rob them if you only toss food in once and walk away.

• Staples: sinking micro pellets, small wafers broken into pieces
• Frozen: baby brine shrimp, daphnia, cyclops, chopped bloodworms (not huge chunks)
• Live (if you do it): baby brine shrimp, microworms, grindal worms

I like to do small amounts more often rather than one big dump. You’ll see them “pepper” the bottom and plants, hunting all day. If their bellies look a bit pinched, they’re probably getting outcompeted.

4) Behavior and tankmates

They’re schooling cories with a twist: they do a lot of midwater hovering and little darting runs, not just bottom shuffling. In a good-sized group they act totally different—more confident, more visible, and way more fun to watch.

• Best tankmates: small peaceful fish (ember tetras, chili rasboras, small pencilfish), small gourami species, otos
• Shrimp: usually fine with adult shrimp; babies may disappear
• Avoid: big/boisterous fish, fin nippers, anything that treats “tiny fish” as a snack

They’re also surprisingly sensitive to stress from constant chasing. If you see them glued to corners or hiding nonstop, it’s usually tankmates, not shyness.

5) Breeding tips (if you want to try it)

They’re one of the easier cories to breed once they’re settled, fed well, and you’re doing regular water changes. Spawning often kicks off after a cool-ish water change and heavy feeding for a week or two.

• Conditioning: frozen/live foods for 1–2 weeks (daphnia and baby brine are great)
• Trigger: a water change with slightly cooler water plus fresh, clean water
• Egg spots: glass, plant leaves, filter intake, even the heater sometimes

If you actually want fry, you’ll get better results pulling the eggs or moving the adults. Adults aren’t unstoppable egg-eaters, but they’ll snack if they find them.

6) Common problems to watch for

Most pygmy cory issues come from three things: dirty substrate, sharp substrate, or not getting enough food. They’re tough little fish, but they don’t love swings or neglect.

• Barbel wear/infections: usually rough gravel or a dirty bottom—swap to sand and improve maintenance
• Skinny fish: outcompeted at meals; feed smaller sinking foods and try night feeding
• Staying hidden all the time: group too small, tank too bare, or tankmates too active
• Sudden losses after changes: big parameter swings; do smaller, more frequent water changes
• Ich/other stress bugs: often show up after new fish or stress—quarantine newcomers if you can

If you keep them in a stable, planted tank with a soft bottom and a real group, they’re honestly one of the most rewarding “small fish” you can buy. The key is treating them like the main character, not a side quest.