Slate cory
Hoplisoma concolor
The Slate cory features a streamlined body with a slate-gray coloration and distinctive dark spots along its flanks.
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About the Slate cory
Corydoras concolor is that deep slate-gray, chunky little cory that looks almost like a moody, high-backed cousin of the bronze cory. Give them a soft sand bottom and a group to hang with, and you will see those neat rusty-orange fin flashes when they are comfortable. They are bottom cruisers that spend all day sifting and snuffling for food, and they will dart up for air now and then (totally normal).
Also known as
Quick Facts
Size
5.4 cm SL
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
20 gallons
Lifespan
5-10 years
Origin
South America (Orinoco River basin)
Diet
Omnivore - sinking pellets/tablets, frozen foods (bloodworms, daphnia), live foods; will also take quality flakes
Water Parameters
22-26°C
6-8
2-25 dGH
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Calculate heater sizeCare Notes
- Keep them in a real group - 5+ is where they stop acting skittish and start cruising the bottom like they own it.
- Sand is the move; sharp gravel will beat up their barbels and you will start seeing a sore-looking mouth and less foraging.
- They do best in soft to moderately soft water with a slightly acidic to neutral pH (about 6.0-7.2) and steady temps around 74-79F.
- Feed after lights-out sometimes: sinking micro pellets, wafers, and frozen foods like bloodworms/daphnia get them fat and active, and they will miss out if faster fish steal everything.
- They are peaceful with small community fish (tetras, rasboras, peaceful dwarf cichlids), but skip fin-nippers and anything big enough to treat them like snacks.
- Give them cover and flow: plants, wood, and a few shaded spots plus decent filtration makes them way more confident, and they will spawn more often.
- Breeding tip: a cool water change and a heavier feeding run often triggers eggs on glass or plants; pull the eggs or the adults will snack on them.
- Watch for the usual cory issues - barbels eroding from dirty substrate, rapid breathing if oxygen is low, and never mix them with salt or harsh meds unless you know they are cory-safe.
Compatibility
Good Tankmates
- Small, chill tetras (neons, embers, rummynose) - they stick to midwater, dont bug the corys, and the corys just do their little sand-sifting thing underneath.
- Rasboras (harlequin, chili, lambchop) - peaceful schoolers that wont compete much at the bottom, and they handle the same general community setup.
- Dwarf cichlids that are actually mellow, like a pair of German blue rams - usually fine as long as you give the corys floor space and dont drop them into a spawning war zone.
- Small peaceful livebearers (endlers, guppies, platies) - generally fine, just make sure food reaches the bottom because livebearers can be little pigs at feeding time.
- Other gentle bottom buddies like otocinclus - they dont mess with corys, and both appreciate clean water and a calm community vibe.
- A calm centerpiece like a honey gourami - they mostly cruise up top and ignore the cory group, which is exactly what you want.
Avoid
- Big or pushy cichlids (convicts, most medium-large Africans, jack dempsey types) - slate corys are peaceful and get stressed, chased, or flat-out eaten once the other fish gets size and attitude.
- Nippy fin-biters like tiger barbs or serpae tetras - the corys arent built for drama, and constant harassment keeps them hiding instead of foraging.
- Red tail sharks and other territorial bottom bullies - they claim the whole floor and will run corys off food and resting spots all day.
- Anything that sees them as a snack (adult angelfish can be iffy, big gouramis, big catfish) - once the tank mate has the mouth for it, corys are on the menu, especially at night.
Where they come from
Slate corys (Corydoras concolor) come from South America, mostly in darker, tannin-stained waters where the bottom is leaf litter, roots, and fine silt. That background explains a lot: they appreciate subdued light, plenty of cover, and a soft-ish, clean bottom they can sift all day.
Setting up their tank
If you want these guys to look relaxed and actually come out, build the tank around the bottom. A 20 long is a nice footprint for a group, but bigger is always easier to keep stable.
- Group size: 6 minimum, 10+ is where you really see natural schooling and confidence
- Substrate: fine sand is my pick (they dig constantly); smooth small gravel can work but avoid sharp stuff
- Hardscape: driftwood, leaf litter (catappa/oak), and a few plants that give shade (crypts, swords, floating plants)
- Filtration: gentle flow; sponge filter or a canister with the spray bar aimed along the back works well
- Lighting: dim to moderate; they color up better when they have shaded spots
- Lid: they can dart up for air and spook-jump, so cover gaps
Sand makes a bigger difference with concolor than with a lot of corys. On sand they sift like little vacuum cleaners and you see less barbel wear over time.
Water-wise, they do well in the usual cory range. I kept mine around 74-78F with neutral to slightly acidic water. What they react to most is dirty substrate and swingy parameters, not chasing a perfect number.
They are sensitive to sudden big changes. If you are doing a big cleanup, do it in stages: half the substrate one week, the other half the next.
What to feed them
They are not algae eaters. Think small meaty stuff plus a decent sinking staple. If you only drop in flakes for the community, the slate corys will survive, but they will stay skinny and shy.
- Staples: sinking wafers or pellets made for catfish/corys (small enough for them to mouth easily)
- Frozen: bloodworms, blackworms, daphnia, brine shrimp, chopped mysis (rotate)
- Live (if you can): blackworms, grindal worms, baby brine for conditioning
- Extras: a tiny bit of Repashy-style gel foods can be great if your tank has faster eaters
Feed after lights-out or in a dim corner if you keep them with hungry midwater fish. I use tongs to drop food right onto the sand where the corys are browsing.
A couple small feedings beats one big dump. You want them rooting around with full bellies, not leaving piles that rot under the decor.
How they behave and who they get along with
Slate corys are peaceful, a little on the shy side, and way more fun in a real group. In a small group they tend to hide and only come out in bursts. In a bigger group they cruise the whole bottom and do that classic cory 'shuffle' through the sand.
- Good tankmates: small tetras, rasboras, pencilfish, hatchetfish, peaceful dwarf cichlids, small calm gouramis
- Also good: other gentle bottom fish if the tank is big (otos, small plecos), but avoid crowding the floor
- Avoid: fin-nippers, boisterous barbs, large cichlids, crayfish, and anything that will outcompete them at feeding time
You will see them dash to the surface for a gulp of air now and then. That is normal for corys. If they are doing it constantly, check oxygenation and gunk buildup.
Breeding tips
They can be bred at home, but concolor can be a little more "fussy" than the super common bronze/peppered types. The big triggers for me were heavy feeding for a week or two and then cooler water changes that mimic rain.
- Conditioning: feed frozen/live foods regularly for 1-2 weeks
- Trigger: 30-50% water change with slightly cooler water, plus extra aeration
- Spawning: look for the classic T-position and then eggs on glass, plants, or hardscape
- Egg handling: adults may snack on eggs, so either pull the parents or move the eggs
- Hatching: typically a few days depending on temperature; keep flow gentle and water very clean
- Fry food: first foods like microworms, vinegar eels, or baby brine once they can take it
If you want higher hatch rates, add a little methylene blue in a separate hatch container or use an airstone and manually remove any white (fungused) eggs each day.
Common problems to watch for
Most issues I have seen with slate corys come back to the bottom getting dirty, rough substrate, or them getting bullied off food. They are hardy once settled, but they do not love a neglected substrate.
- Barbel erosion: usually from sharp gravel or dirty, compacted substrate; switch to sand and keep the bottom cleaner
- Skinny corys: not getting enough food in a community tank; target feed sinking foods
- Gill irritation and flashing: often from poor water quality or sudden parameter swings; test, do steady water changes, add aeration
- Ich/velvet: they can catch it like any community fish; raise temp carefully (if appropriate) and treat the whole tank
- Stress from meds/salt: corys can react badly to heavy salt use and some harsh meds; research dosing and go slow
Skip "shotgun" dosing. If a slate cory looks off, check ammonia/nitrite first, then nitrate, then look at temperature and oxygen. Fix the cause before reaching for meds.
One last thing: keep a close eye the first couple weeks after you bring them home. They can come in a bit thin, and a calm, dim tank with regular small feedings helps them settle in fast.
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