Julii Cory Catfish Care: An Expert’s Guide

Corydoras Julius or Corydoras julii is a peaceful, beautiful and relatively easy to care for fish. In this guide, you will learn about the intricate history of this species and how to care for this unique brown catfish.

short information

wild habitat Northeast Brazil, small rivers and streams
The size <2 inches (5 cm) Females are 0.2 inches larger than males.
Temperament Calm, peaceful
tank size >20 gallons (75 liters)
Diet Carnivorous, feed a variety of sinking pellets and live/frozen foods.
Water 73-79°F (23-26°C) pH: 6.0-7.5
Complexity Need some experience
Etymology “Kori”: comes from the Greek word “Korus”, which means a helmet, “dora”: skin. julii: enigmatic personality

About the author: Thijs is an aquarium enthusiast who writes on his blog KeepingCatfish.com, where he writes about the care of aquarium catfish such as cory catfish and pleco catfish. He is also the author of one of his hobby projects, the Wild Betta blog, where he promotes the little known wild betta fish.

In wild nature

This species of catfish lives in the northeast of Brazil, in the province of Piauí. Corydoras julii lives in small and medium-sized rivers with sand and gravel substrate.

Their light skin color and dots camouflage them perfectly in these habitats. Their nickname “Leopard kori” also comes from this unique pattern.

They live in schools ranging from a few individuals to hundreds or even thousands of fish to protect themselves from predators.


Corydoras julii is easily identified by the spots all over its body. It has a stripe down the middle of its body that reaches about half of its body. Cory catfish Julii reaches about 2 inches in length, males remain smaller than females.

The dorsal fin of Corydoras julii is transparent, about half of it is covered with a black dot.

Julii Cory catfish belong to the genus Corydoras. These fish get their name because they don’t have scales, but instead have armored plates all over their body.

Corydoras julii versus Corydoras trilineatus.

If you are reading this article, chances are you don’t have Corydoras julii in your tank, but Three-line corridor or three-lane catfish. These two fish are very similar, especially for beginners. Because of this confusion, hobbyists like to give C. trilineatus another nickname, “false catfish julii cory”.

However, there are some clear differences between both species:

Stripe in the middle C. trilineatus, also called trilinear kori, has a prominent black line covering the entire length of the body to the base of the tail. In C. julii this line is shorter and paler.

dot pattern – Corydoras julii has not stolen its name “leopard measles”. Unlike C. trilineatus, C. julii has more, usually smaller, distinct spots all over its body. In the head area, these spots become more visible and brighter. On the other hand, three-row kori has a more reticular mesh pattern.

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The size – C. julii remains smaller than C. trilineatus, reaching 2 inches and 2.5 inches respectively.

Pet stores often use the name “Julius cory” to sell Corydoras trilineatus because it sells better. Thus, real julii cory catfish are actually a very rare sight in the hobby because they are not often bred and rarely harvested.

In addition, Corydoras julii species can be crossed with Corydoras trilineatus, as they are both part of pedigree 9. Unfortunately, this reduces the pool of pure Corydoras julii, further confusing the hobby.


Kori catfish Julii have the same aquarium requirements as other pygmy catfish.

Most species of catfish need an aquarium of at least 20 gallons, including C. julii. Only a select few small catfish, such as pygmy catfish, can live in a 10 gallon aquarium.


Since the catfish themselves do not produce much waste, the recommended filtration depends on the tankmates you wish to keep with the catfish.

If you decide to build a dedicated breeding tank, a sponge filter is one of your best options: it filters biologically, it’s cheap and low tech.

If you keep them with a lot of other fish or large contaminants like catfish, a stronger filter is recommended. I recommend a filter that cleans at least 6 times the volume of the tank per hour.

Plants and decor

Live plants are a great addition, and I would even go so far as to say that they are essential for your brown catfish. They greatly improve water quality and provide a natural hiding place for your fish. It doesn’t matter which species you use, but you can read the beginner’s guide to aquarium plants to learn more.

Wild-caught toothy catfish have been known to prefer live plants over glass or spawning crowds, and they sometimes spawn only on these plants.

If you want to learn more about the best plants for catfish, this blog has a complete guide. You can read it here.


We’ve come to the rather controversial part of keeping gray catfish: choosing a gravel species.

The best gravel for measles catfish is sand, but round gravel is also fine. The reason for this is that brown catfish have sensitive antennae that can be damaged by sharp gravel.

Although it may seem like a trifle, in the beginning, constant exposure causes micro-erosion, which eventually leads to the death of the tendrils.

These barbels are critical for finding food, and if your catfish doesn’t have them, it can cause sickness and possibly even death.

Where is the controversy, you ask? Well, some experts pointed out, including Corey from cooperative game “Aquarium”, this brown catfish is known to inhabit habitats with sharp gravel. This substrate consists of a mixture of sand, rocks and sharper pebbles.

While this may be the case in some wild habitats, it is much safer to choose a rounded or sandy substrate. After all, this has the least possible risk of harming the barbels.

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If you are using sharper gravel, do not feed food that quickly breaks into pieces or easily gets into the gravel. This food will make the koria catfish dig into the substrate. The same goes for most live foods, as larvae, such as bloodworms, burrow into the substrate.

Although sharp gravel can have a negative effect on barbels, poor water quality and bacterial infections in the substrate are also a serious cause of barbel erosion in brown catfish. Therefore, regular filter cleaning and regular water changes are a must.

tank mates

In general, Julia’s catfish is a very peaceful species of fish that can live with a large number of other fish. C. julii does not do well with overly competitive species such as cichlids or thorns. While it can certainly be done with some preparation, it is not recommended for beginners.

Here are some examples of suitable aquarium mates for common catfish:

Cory catfish should always be kept in groups of the same species. This means that Corydoras julii should always be kept in a group of 6 or more fish. Otherwise, these fish are stressed and will not show their full potential.

Mixing catfish is possible, but then the same rule applies: keep at least 6 specimens of the same species. Another thing to watch out for is interbreeding. Cory soma Julii can interbreed with other strain 9 species, so avoid placing these species with Corydoras julii.

Water parameters

Most heart-shaped catfish are quite tolerant of water parameters and can live in a wide variety of conditions. Catfish Julius is also not picky about water parameters, although he prefers slightly acidic water.

The ideal water temperature for Julii catfish is 73-79°F (23-26°C), unlike some kori catfish that do not need a heater, this species definitely needs a heater. Julii catfish do well at a pH of 6-7.5. Ideal GH and KH values ​​are between 4 and 8, but softer water is more like their natural environment.

Wild-caught Corydoras julii tend to be more sensitive to water parameters and like lower pH (more acidic) and generally softer water. This can be achieved by adding reverse osmosis water or (well-filtered) rainwater. Another natural alternative is Indian almond leaves, which will add a natural touch to your aquarium.


It is important to note that common catfish do not feed on algae and cannot only feed on food leftovers from other fish. Since they are not competitive and can only eat the food that is on the bottom, all other fish will eat that food before they have a chance.

The Julii cory is an omnivore, but it does best on a high protein diet. In the wild, they eat various insect larvae, worms, and other small invertebrates.

Cory catfish should be fed their own diet, preferably a varied diet of various pellets. Cory catfish also love live foods such as bloodworms, black worms, and mosquito larvae.

Since not everyone has access to live food, Hikari pellets are a great alternative. I discovered Hikari Carnivore Granules as well as Sinking Hikari Wafers be great. I also love Turnip products. Alternatively, you can feed them Algae Wafers or Spirulina Wafers to feed them extra nutrients.

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Breeding Corydoras julii is similar to breeding other catfish species. Breeding brown catfish can usually be divided into three stages:

  1. Conditioning
  2. Dry season simulation
  3. rainy season simulation

Determining the sex of catfish julii cory

The females of Corydoras julii are fuller and fatter than the males. They also tend to be slightly larger. In particular, after careful handling of these fish, you will be able to clearly see the difference (if your sea catfish reached maturity at about 9 months of age).

The ideal ratio for breeding Julii cory catfish is one female to two males because this increases the chances of fertilization.

It is important to know that whether the common catfish spawns strongly depends on specimens, water parameters and many other conditions. Achieving success in breeding can be either very simple or require significant effort, sometimes inexplicable.

However, in most cases, breeding Corydoras julii is fairly easy with this three-step process. You can take this process as far as you like, depending on how easy your catfish is to breed.

  1. Conditioning Measles Catfish Julii

Within two to three weeks, you should increase feeding and switch to live food (or frozen if you can’t find it). Feed preferably in small portions two to three times a day. Good live foods are black worms, bloodworms, grinders and mosquito larvae.

During this time, the goal is for the female to gain weight and produce eggs. This extra food will stimulate reproduction and start the natural breeding cycle.

  1. Dry season simulation

This is the season in the Amazon when food becomes scarce and temperatures rise. The water level also drops, and brown catfish go into “survival” mode.

You can simulate this on a small scale by increasing the water temperature by a few degrees (gradually, don’t boil the fish!) and lowering the water level in the aquarium by up to 50%.

I recommend doing this for three to seven days. Stop feeding or reduce the amount of feed at this time for optimal results.

  1. rainy season simulation

This season, common catfish spawn naturally. Fresher and cooler water flows into the rivers, and heavy rains fill the streams, and there is more food.

This can be recreated on a small scale by filling your aquarium tank with slightly cooler water. If this is not enough, you can continue to change the water in the aquarium.

If your breeding attempt is successful, you will see how the common catfish lays eggs on the glass. Place the eggs in a separate container for optimal success. After that, the fry can be fed with baby brine shrimp.


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