By Hannah NielsenWhy this guide exists
You searched "bronze corydoras", and I'd bet good money you've already been handed the worst advice in the hobby: "get a couple of cories, they'll keep the bottom clean." That single sentence is responsible for more slowly starved, barbel-worn, lonely catfish than almost anything else I see.
I'm Hannah Nielsen — I photograph and write our planted-community and shoaling-fish guides from my flat and studio in Cambridge, and a group of bronze cories has lived along the bottom of one of my display tanks for years. They're the first bottom-dweller I recommend to anyone, and the one most often kept badly through no fault of the keeper. This guide is the honest version: how many to buy, what they actually eat, why the substrate under them matters more than almost anything, and which cories we currently have in stock.
A bronze corydoras (Corydoras aeneus). That iridescent coppery-green patch along the flank is structural colour — it shifts as the fish turns, which is exactly why a settled group catches your eye as they potter. Product photo · our warehouse.
Five things most UK guides never tell you
- They breathe air — on purpose. Bronze cories are facultative air-breathers. They dart to the surface, gulp a bubble of atmospheric air, and absorb oxygen through a modified, blood-rich section of the intestine before passing the spent air out the vent [2]. A healthy cory does this from once to dozens of times an hour — it's normal, not a sign of suffocation.
- They genuinely coordinate as a group. A peer-reviewed study of Corydoras aeneus showed that familiar fish actively shape how the group moves and stays together — these aren't fish that merely tolerate company, they cooperate [3]. That's the science behind the "keep six or more" rule.
- The barbels are taste organs you can destroy. Those little whiskers around the mouth are packed with taste buds and used to root for food in the substrate. Sharp gravel plus poor water quality erodes them away [4], and a cory that's lost its barbels struggles to feed for the rest of its life.
- They're armoured, not scaled. Corydoras belong to the family Callichthyidae — the "armoured catfishes" — and their bodies are protected by two rows of overlapping bony plates rather than ordinary scales [1]. It's where the family name comes from.
- They're a long-lived bargain. For a fish that often costs less than a pint, a well-kept bronze cory can share your tank for 5 to 10 years [4]. Few community fish at the price last anywhere near as long.
Bronze vs the other common cories: which is right for you?
"Corydoras" covers dozens of species in the trade, and they are not interchangeable — size and substrate footprint vary a lot. Here's the honest comparison between the bronze and the other cories you'll meet most often.
| What matters | Bronze (C. aeneus) | Albino (aeneus strain) | Panda (C. panda) | Pygmy (C. pygmaeus) |
|---|---|---|---|---|
| Adult size | ~6.5 cm | ~6.5 cm | ~5 cm | ~2.5 cm |
| Look | Coppery-green flank | Pink-white body, pink eyes | White with black patches | Tiny, silver, mid-water |
| Tank size | 60 L+ | 60 L+ | 60 L+ | 40 L+ (nano) |
| Hardiness | Very hardy | Very hardy | Slightly more sensitive | Hardy but tiny |
| Best for | First bottom-dweller | First bottom-dweller | Cooler planted tanks | Nano shoals |
If you want the toughest, most forgiving starter cory, the bronze (or its albino form) is the one. Want something smaller for a nano tank? Go pygmy. All share the same core care — group of six, smooth sand, their own food [4].
The cories we currently stock
The bronze and its close Venezuelan relatives are the everyday workhorses — hardy, sociable and happy in hard UK water. These are our current in-stock bronze-type cories:
The long-fin and Venezuelan-orange forms are the same easy fish underneath — you're choosing a look, not a harder animal. If this is your first bottom-dweller, any of them will do beautifully.
Bronze cories are not a clean-up crew, and they do not live on the food other fish miss. They are omnivores that need their own sinking food delivered to the bottom every day [4]. Treating them as a self-feeding tank gadget is the number-one welfare mistake — you'll see hollow, sunken bellies and a short, unhappy life. Feed them properly and they thrive for years.
How many to buy, and the shoal rule
Bronze cories are shoaling fish in the truest sense — research on the species shows familiar individuals actively coordinate how the group moves and feeds [3]. The practical upshot: keep six or more of the same species, and ideally more. A pair or trio spends its life hiding; a proper group is out in the open, patrolling the sand together, often resting in companionable little piles.
A six-fish starter shoal in a 60-litre tank is a lovely, balanced setup. Floor space matters far more than height for a bottom-dweller, so a longer, shallower tank beats a tall narrow one every time [4].
For a first cory shoal I run a 60-litre with a smooth sand bed (pool-filter sand or fine play sand, rinsed well), a few smooth pebbles and some Java fern and Anubias on wood for cover. Fill with dechlorinated hard tap water, heater set to 23–24 °C, gentle filter. Add six bronze cories and feed a sinking wafer or some frozen bloodworm to the bottom each evening after the mid-water fish have settled. That's it — no special chemistry, no fuss.
The substrate question: why smooth sand wins
This is the bit most beginner setups get wrong. Cories feed by taking mouthfuls of substrate, sifting out the food, and rooting around with the delicate sensory barbels at the corners of the mouth. On smooth sand this works perfectly. On sharp, coarse gravel — especially in a tank where detritus builds up — those barbels abrade and wear down over time [4], and a cory that can't feel its food can't feed efficiently.
If you're setting up specifically for cories, choose smooth sand. If you've already got rounded gravel and don't want to strip the tank, keep it scrupulously clean and watch the barbels — but for a new tank, sand is the clear winner.
Tank mates that actually work
A bronze cory occupies the bottom zone most community fish ignore, which makes it one of the most compatible fish in the hobby. These are companions I keep with cories and trust:
- Neon tetras and other small tetras — peaceful mid-water shoalers that share the same water and leave the substrate to the cories.
- Harlequin rasboras — calm, colourful and perfectly matched to a community bottom shoal.
- Honey gouramis — gentle surface-oriented fish that fill the top of the tank without bothering anyone.
- Cherry shrimp — thrive in the same hard water; adult shrimp are safe alongside peaceful cories.
Avoid: large or aggressive cichlids and fin-nippers that could harass a slow, peaceful, bottom-bound catfish [4].
Watch: corydoras working a planted tank
Transcript / what you're seeing (0:00–0:20): corydoras methodically sift the substrate and graze across leaves and wood in a planted tank, occasionally darting up toward the surface. That surface dash is the air-breathing behaviour [2] — normal, not distress. Notice how the fish work the bottom as a loose group rather than scattering: that out-in-the-open, coordinated pottering is the tell-tale of a settled, properly sized shoal.
Sexing and breeding
Sexing is straightforward once they mature: females are noticeably larger, rounder and broader across the body — viewed from above the difference is obvious — while males stay slimmer and a touch smaller. Bronze cories are one of the easier egg-layers to breed at home: a well-fed group often spawns after a cool water change, the females carrying clutches of eggs in a "pouch" formed by the pelvic fins and pressing them onto glass, plants and wood [6]. No intervention is needed to trigger it beyond good food and stable conditions.
A corydoras feeding with its barbels down against the substrate. This is exactly the rooting behaviour smooth sand protects — and sharp gravel slowly ruins. Product photo · our warehouse.
What to look for when you buy (anywhere)
Whether you buy from us or anyone else, these are the welfare markers that separate a healthy cory from a problem one:
- Intact, full barbels. Look closely at the whiskers around the mouth — they should be long and complete, not stubby or eroded. Worn barbels are a sign of a poor substrate or dirty conditions [4].
- A rounded (not sunken) belly. A hollow, caved-in stomach is the classic underfed-on-leftovers look. Healthy cories are pleasantly plump.
- Active and out in the open in a group. Settled cories potter about together. Fish clamped in a corner, or a single cory alone in a tank, are red flags.
- Clean, complete fins with no white fuzz, clamped edges or split rays.
- Ask which species. A seller who can tell you it's Corydoras aeneus (and not a lookalike) is a seller who knows their stock [1].
Community & clubs
Corydoras have a passionate, knowledgeable UK following, and the best place to learn species ID and source rarer lines is the hobby itself, not a shop shelf:
- The Catfish Study Group is the UK society specialising in catfishes, including Corydoras and their relatives — the place to learn species identification, see proper biotope setups and meet breeders.
- Corydoras World (corydorasworld.com) is a dedicated corydoras community and reference, invaluable for telling the many lookalike species apart and following the constant taxonomic reshuffles in the genus.
When your cories arrive: acclimation
Bronze cories are hardy and forgiving, but as a bottom-dweller they can't dart to a different water layer to escape a sudden change — so take the drip gently, especially moving into hard UK tap water [5]:
- Float the sealed bag in your tank for 15–20 minutes to equalise temperature.
- Drip-acclimate for 30–40 minutes at a slow drip, roughly doubling the bag volume before you net them out — a bottom fish equilibrates more slowly to a pH or hardness shift.
- Have sand and cover in place on day one. A soft substrate to root in and some planting or wood for shade dramatically cut transport stress.
- Net the fish into the tank rather than tipping in the transport water.
- Lights off for a couple of hours afterwards, and don't feed for the first 24 hours — it keeps water quality stable while they settle.
Ready for more?
- Learn: our corydoras care guide for the full husbandry deep-dive, and the pleco care guide for the other peaceful bottom-dweller that pairs beautifully with a cory shoal.
- Compare: the albino corydoras guide if you fancy the pink-white form of this exact fish, the julii corydoras guide for the spotted cory (and the honest truth about what's really sold as "julii"), or the pygmy corydoras guide and panda corydoras guide for the smaller species.
- Shop: browse the corydoras hub and the wider catfish & plecos hub for everything that thrives on the bottom of a UK community tank.
