The San Juan Cory (recently reclassified as Gastrodermus bilineatus) is a small, attractive, and peaceful armored catfish native to the Madeira River basin in Bolivia. It features a striking pattern of white stripes along a dark body. Like all Corydoras, they are obligate air-breathers and social bottom-dwellers that must be kept in schools. They require a soft sand substrate to protect their delicate sensory barbels.
San Juan Cory At a Glance
San Juan Cory Tank Requirements
Will San Juan Cory fit in your tank?
Care guides tell you what San Juan Cory needs, the next question is whether your tank can safely provide it. Test San Juan Cory against your tank size, maintenance needs, and the fish you already keep before you buy.
San Juan Cory Water Parameters
San Juan Cory Temperament & Compatibility
San Juan Cory Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard / Unsexed
Typically sold unsexed in the aquarium trade. As schooling fish, a group of 6 or more is essential for their well-being and to encourage natural foraging behaviors.
Same care requirements as the base species
Also known as: San Juan Corydoras, Juvenile
Female
Females are noticeably larger, broader, and more robust than males, especially when viewed from above or when carrying eggs.
Differs in 1 trait from base species
Also known as: Female
Male
Males are slimmer and slightly smaller than females. They possess more pointed ventral fins.
Differs in 1 trait from base species
Also known as: Male
San Juan Cory Care Guide Summary
The San Juan Cory, scientifically known as Corydoras bilineatus, belongs to the Catfish family group. Adults reach a maximum size of approximately 4.5 cm and have a fusiform body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the bottom zone of the aquarium and produces a low level of biological waste.
To thrive, the San Juan Cory requires a freshwater only aquarium with a minimum volume of 60 litres and a tank length of at least 60 cm. Water temperature should be maintained between 22°C and 26°C, with a pH range of 6–7.5 and a general hardness of 4–18 dGH. A low water flow is preferred.
The San Juan Cory is a rewarding species to keep, provided its core environmental needs are met. This species is available in 3 varieties: Standard / Unsexed, Female, and Male. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
San Juan Cory Habitat Setup
When setting up an aquarium for the San Juan Cory, a low water flow best suits their natural preferences. Because this species occupies the bottom zone, the aquarium layout should prioritise sufficient floor space with hiding spots among rocks, wood, or dense planting. Useful additions include a sand substrate to accommodate their sifting behaviour and smooth gravel or rounded substrate to protect their sensitive barbels. Keepers should note that expect substrate disturbance, so lightweight décor should be secured.
San Juan Cory Compatibility Notes
Classified as peaceful, the San Juan Cory is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the bottom zone can help reduce competition and territorial overlap.
Who San Juan Cory Is Actually For
San Juan Cory is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide a keeper who can commit to a proper group of at least 6. It makes the most sense for a hobbyist who will actually build around its needs, especially sand.
The most common mistake is treating San Juan Cory like any other community fish and skipping the soft sand it needs to forage safely. Another frequent problem is underestimating its social needs. A token pair or trio often behaves very differently from a real group.
San Juan Cory Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for San Juan Cory.
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
36 Gallon Bowfront
40 Gallon Breeder
Show 19 more tank sizes
Frequently Asked Questions About San Juan Cory
How big does San Juan Cory get?
San Juan Cory (Corydoras bilineatus) typically reaches a maximum adult size of approximately 4.5 cm. They have a fusiform body shape and a moderate growth rate.
What tank size does San Juan Cory need?
A minimum aquarium volume of 60 litres and a tank length of at least 60 cm are recommended for San Juan Cory. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does San Juan Cory need?
San Juan Cory thrives in freshwater only conditions with a temperature range of 22–26°C, a pH between 6 and 7.5, and a general hardness of 4–18 dGH. A low water flow is preferred.
Is San Juan Cory peaceful or aggressive?
San Juan Cory is classified as peaceful with an aggression score of 0 out of 10. They are generally well-suited to peaceful community tanks.
How many San Juan Cory should be kept together?
San Juan Cory is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does San Juan Cory have any special tank requirements?
Yes. San Juan Cory benefits from sand (sifters) and smooth gravel (sensitive barbels) in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Useful setup supplies
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- May 11, 2026
- Last updated
- May 11, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for San Juan Cory
These fish are strong compatibility matches for San Juan Cory based on water preferences, temperament, adult size, and tank behavior.
Kabia rainbowfish
Glossolepis kabia
Ideal Tank MatesScissortail Rasbora
Rasbora trilineata
Ideal Tank MatesRosy Red Minnow / Fathead Minnow
Pimephales promelas
Ideal Tank MatesRose Danio
Danio roseus
Ideal Tank MatesSunset Platy (Variatus Platy)
Xiphophorus variatus
Ideal Tank MatesWestern Rainbowfish
Melanotaenia australis
Ideal Tank MatesPlants That Suit San Juan Cory
These plants pair well with San Juan Cory based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Amazon Frogbit
Limnobium laevigatum
Asian Watergrass
Hygroryza aristata
Asian Watermoss
Salvinia cucullata
Carolina Mosquito Fern
Azolla caroliniana
Common Duckweed
Lemna minor
Crystalwort
Riccia fluitans
Fish Similar to San Juan Cory
Agassiz Cory
Corydoras agassizii
A peaceful, bottom-dwelling armored catfish native to the Amazon River basin. They are easily identified by their silvery body with dark spots and a distinct black mask over their eyes. Like all Corydoras, they are highly social and must be kept in groups. A soft sand substrate is absolutely essential to protect their delicate sensory barbels as they forage.
Skunk Cory
Corydoras arcuatus
A charming and peaceful bottom-dwelling catfish native to the Amazon basin, easily identified by the dark, skunk-like stripe running from its mouth along the ridge of its back to its tail. Like all Corydoras, they are obligate shoaling fish that require a group of conspecifics to feel secure. Fine sand substrate is mandatory to prevent damage to their delicate sensory barbels.
Loxozonus Corydoras (C079/C082)
Corydoras loxozonus
A peaceful, bottom-dwelling catfish native to the Rio Meta basin in Colombia. Known for the distinctive diagonal black stripe across its back and a mask over its eyes. Like all Corydoras, they are highly social and must be kept in groups. A soft, sandy substrate is strictly required to prevent damage to their delicate barbels as they sift for food.
Black Fin Cory
Corydoras leucomelas
A peaceful schooling catfish native to the Amazon basin, easily identified by its black dorsal fin and a dark mask-like band across its eyes. Like all Corydoras, they are bottom-dwellers that use sensitive barbels to forage. They possess a modified intestine allowing them to gulp atmospheric air, so occasional darts to the surface are normal. They are highly social and require a soft sandy substrate to prevent barbel erosion.
Olga Cory
Corydoras simulatus
The Olga Cory is a peaceful, long-snouted schooling catfish from the Meta river basin in Colombia. It features a creamy bronze body with a distinct dark band running along its back and a vertical stripe over the eye. Like all Corydoras, it is an energetic bottom-dweller that requires fine sand to sift through without damaging its delicate barbels.
Bandit Cory
Corydoras metae
A highly social, peaceful bottom-dwelling catfish endemic to the Rio Meta basin in Colombia. Instantly recognizable by the black 'bandit' mask over its eyes and the dark ridge stripe along its back. Like all Corydoras, they must be kept on a soft sand substrate to prevent severe damage and infection to their sensitive foraging barbels. They are schooling fish that require groups of at least 6 to thrive and display natural behavior.