Julii Corydoras Fish Species Profile

Characteristics, Origin, and Helpful Information for Hobbyists

Corydoras julii fish

Martin Siepmann / imageBROKER / Getty Images

Julii corys are cute bottom dwellers that will clean your tank with the sensitive barbels they use to root around for food at night. But any fish attempting to swallow this diminutive catfish will be in for a painful surprise of spikes and armor. This species has the ability to rotate the eye, which gives it the appearance of winking. Hence, fishkeepers often find this fish quite entertaining and endearing.

Species Overview

Common Names: Julii catfish, julii cory, leopard cory

Scientific Name: Corydoras julii, Synonym Corydoras leopardus

Adult Size: 2.5 inches

Life Expectancy: 5 years


Family Corydoradinae
Origin Lower Amazon River in NE Brazil
Social Nocturnal, Peaceful
Tank Level Bottom dweller
Minimum Tank Size 10 gallon
Diet Omnivore, eats all foods
Breeding Egglayer
Care Easy
pH 6.5 to 7.8
Hardiness up to 20 dGH
Temperature 73 to 79 degrees F (23 to 26 degrees C)

Origin and Distribution

Indigenous to the lower Amazon region, primarily the Parnaíba River of Brazil, Corydoras julii is found in flooded forest regions as well as in creeks and small tributaries. It is often confused with Corydoras trilineatus, a species that is found in the upper Amazon.

The region the julii comes from is not heavily fished commercially, so most shops do not carry true julii corys. Although it is quite common to see Corydoras trilineatus incorrectly labeled as Corydoras julii, the true julii cory will only occasionally be seen for sale in fish shops through hobby breeding.

Colors and Markings

Many owners who think they have taken home the julii cory, Corydoras julii, have accidentally purchased Corydoras trilineatus. Julii corys are smaller and more stout in build, with a shorter head and rounded snout. They also have small, isolated spots, while Corydoras trilineatus has spots that tend to connect into a reticulated pattern; this is particularly noticeable on the head. This species reaches an adult size of a bit over 2 inches.

Like other cory species, the body is silvery gray. A dark zigzag stripe runs along the lateral line from the gills to the tail. Above and below this dark line is a section that is not spotted, beyond which are many small dark spots of varying size. On the body, some of these spots connect to form short lines, but on the head, the spots are distinctly separate, a feature that differentiates this species from similar corys.

The dorsal fin is transparent with a large black blotch on the upper fin that does not extend down into the body. The caudal fin has vertical rows of dark brown spots that give the appearance of striping. The anal, adipose, pectoral, and ventral fins also have these spots, but they are much paler in color than on the caudal fin. Instead of scales, this species has overlapping hard plates, known as scutes; hence it is called an armored catfish.


As with many members of the genus, Corydoras, this species must be kept in a school of at least four or more. They get along well with other small catfish as well as small peaceful fish. Possible tankmates include small members of the tetra family, danios, rasboras, dwarf cichlids, as well as any small community fish. Avoid any large or aggressive fish.

Julii Corydoras Habitat and Care

Juliis are undemanding and tolerate a range of initial water parameters. Water can be slightly acidic to slightly alkaline, with soft to medium-hard water hardness. However, they are sensitive to poorly maintained tanks, especially those with a dirty substrate and few water changes, resulting in deteriorating water chemistry. Water must be well-filtered and oxygenated.

The substrate should be soft, as this fish will scavenge the bottom for bits of food. Sand or small, very smooth gravel, is suitable. Driftwood is recommended, as well as anything that can serve as a hiding place. Plants are also needed; floating plants can be used to dim the lighting, as this species does not appreciate bright lights.

Julii Corydoras Diet and Feeding

Very accepting of most foods, this species will consume essentially anything that falls to the bottom. However, don’t assume they are getting enough to eat. It is not uncommon for small bottom-dwelling catfish to starve before their owner recognizes it. To be assured they receive the proper diet, use sinking tablets or pellets as their primary diet. Live foods, such as brine shrimp, daphnia, and bloodworms can be delivered to the bottom via tongs to supplement their diet. Because they are nocturnal, feedings are ideally timed to be just before lights are turned off.

Gender Differences

As with others in the genus Corydoras, sexual differences can best be determined by examining from above. The female will be rounder and broader in the body than the male. Overall the female is larger, and when full of eggs looks noticeably plump in comparison.

Breeding the Julii Corydoras

Breeding of the julii cory is typical of other cory species. A breeding tank is recommended, as the parents will happily consume their eggs and fry, so it is necessary to separate the parents from the eggs after spawning has taken place. If spawning takes place in a breeding tank, the adults can be moved back to the main tank and the eggs left in the breeder tank to hatch and grow.

Use very fine smooth gravel or sand for substrate. A bare bottom is also suitable. Water should be soft, with a slightly acidic to neutral pH (6.5 to 7.0), and at a temperature of approximately 75 degrees F (24 degrees C). Filtration is important but should be gentle enough to not suck small fry into the filter. A sponge filter works well for this type of grow-out setup. Provide a spawning mop or fine-leaved plants such as java moss.

Be aware that this species will readily crossbreed with Corydoras trilineatus, which may or may not be desirable. Some feel crossing the species is degrading the bloodlines, while others find the cross-species an interesting option. When attempting to breed this species, use groups in which there are more males than females. A ratio of at least two to four males for each female is recommended.

Condition the breeder groups with live foods, such as bloodworms or daphnia. Use frozen or freeze-dried counterparts if live foods are not available. When the belly of the female is noticeably swollen with eggs, perform a 50 percent water change with very soft water that is several degrees cooler than the water already in the tank. This will help trigger spawning. If spawning does not occur, continue with daily large water changes as previously described. Increasing aeration will also aid in triggering spawning.

Spawning begins with increased activity, after which the males begin actively pursuing the females. Once a female accepts a male, they will assume a “T-position,” in which the female is positioned with her head against the mid-portion of the male. The male will clasp the barbels of the female with his pectoral fins, while the female forms a basket with her pelvic fins. She will deposit up to four eggs into this basket. It is believed that sperm from the male passes through the gills of the female and are directed to the eggs being fertilized. Once the eggs are fertilized, the female will find a desirable spot and attach the adhesive egg. This process will continue until 100 to 150 eggs have been laid.

Adult julii corys do not guard or care for the eggs once they have been laid. If left in the spawning tank, parents will consume the eggs. To successfully hatch the eggs and raise the fry, it is necessary to separate the eggs from any adult fish.

Another challenge to the eggs is fungal infection. Add a few drops of methylene blue to the water to reduce the chances of losing eggs to fungus. Watch them and remove any eggs that develop fungus, or the fungus will spread and kill all of the eggs. Cherry shrimp may be kept in the tank, as they will consume rotten eggs while leaving healthy eggs alone.

Eggs will hatch in three to five days and should be fed freshly hatched brine shrimp, micro-worms, or rotifers. Very fine fry food is also an option, but as with any food, it is important to remove any uneaten portions promptly. Any deterioration in water chemistry will likely be fatal to young fry.

More Pet Fish Species and Further Research

If you're interested in the julii cory and want to check out similar species, explore other related fish such as:

Check out additional fish breed profiles for more information on other freshwater fish.