Corydoras similis (Smudge Spot Cory)

Corydoras similis

Last updated on July 11th, 2022 at 02:27 pm

The smudge spot cory (Corydoras similis) may be small, but it can live up to its name with the smudge-like blotches on its body and fins. The names smudge spot cory and smudge-spot catfish describe this fish very well because it has distinct dark spots on the front of its body that almost look like smudges of black paint had been applied to the edges of the body and fins.

If you have ever kept fish, then you’ve probably heard of the genus Corydoras and the species Corydoras similis (also known as the smudge spot cory). This peaceful schooling species of catfish originates from Brazil and Argentina. They inhabit small streams and ponds with sandy or silty bottoms where the water current is slow and weak.

Understanding the facts about Corydoras similis (smudge spot cory) will help you be better prepared to care for this fish, whether you’re bringing it home from the pet store or buying it from another owner who purchased it from the pet store. This fish is resilient and can live in a variety of water parameters, as long as they’re not so extreme that they pose a threat to your other fish. Here are some more interesting facts about Corydoras similis (smudge spot cory).

Origin and description

Corydoras similis

Corydoras are a small South American fish species belonging to Callichthyidae family. The name Cory is from the Greek khoros, which means helmet. This is one of two genera in that family with catfish having bony plates on their heads called scutes. The other genus is Brochis, whose members have fewer and larger plates than Corys. The name similis comes from Latin and means like or similar to; it refers to the similarity of markings between Corydoras diphyes and Corydoras similis.

Corydoras similis prefer sandy bottoms rich in aquatic plants such as water hyacinths where they spend most of their time when not feeding at surface level, amongst submerged leaves, or directly underneath floating plants.

Species profile

Corydoras similis

The smudge spot cory is a very small species of catfish native to South America. In fact, it’s one of the smallest known species of Corydoras. It grows to around 6 cm in length and prefers relatively cool water around 76 degrees Fahrenheit. Despite its small size, it actually does well in slightly brackish water for part of each week and doesn’t mind higher levels as long as they don’t last too long.

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Corydoras Similis habitat

They are best kept in tropical freshwater tanks. They will tolerate a range of water conditions but prefer slightly soft, acidic water with a pH between 6.0 and 7.5 and a temperature between 24°C to 28°C (75°F to 82°F). All species are sensitive to drops in oxygen level and will die if exposed to stagnant water or insufficient aeration at low temperatures.

Smudge spot cory size

They can grow to an average size of 6 cm (2.4 inches)

Corydoras similis tank size

The minimum recommended tank size is 20 gallons

Corydoras Similis tank set up

Corydoras similis

The tank must be at least 20 gallons with a pH from 6.0 to 7.2, a water hardness from 10 to 25 dH, and a temperature from 72-78 degrees Fahrenheit. In addition, you will need an air-powered sponge filter, air stone(s), and some plastic plants for your tank. You will also need a heater for temperature regulation purposes.

The lighting is up to you, but 10-12 hours per day should do nicely. Finally, stock your tank with one male and two or three females of species Corydoras Similis, along with some small-leaved plants like Java fern or Anubias barteri var nana; these small fish like dense vegetation where they can hide themselves from other fish in order to avoid predators. A few snails are also appreciated by Corydoras Similis as snacks.

These fish eat algae wafers, flakes, frozen foods such as bloodworms and brine shrimp, freeze-dried foods such as tubifex worms and bloodworms, live worms such as nightcrawlers or blackworms (Lumbricus terrestris), and occasionally even small pieces of meat. Feed them often with a variety for best results!

Corydoras Similis tank mates

Being a shy and peaceful fish, it is not recommended to keep it with boisterous or territorial species. It can be kept in a community tank as long as there are places for retreat. Its size allows it to comfortably live with similar-sized tanks mates like most tetras, dwarf cichlids, and other small catfish. It is important that its tank mates cannot fit inside its mouth and are too big for it to swallow.

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Some other tank mates are Angelfish, Ancistrus, Black Phantom Tetra, Bloodfin Tetra, Buenos Aires Tetra, Cardinal Tetra, Clown Loach, Columbian Shark Catfish, Dwarf Gourami, Flame Tetra, Glowlight Danios, Glowlight tetras, Kuhli Loach, Kissing Gouramis, and Lemon Cichlids.

It is best to avoid keeping it with fish of similar size and temperaments like Discus or larger catfish.

Breeding Corydoras Similis

Corydoras similis

Corydoras species are maternal mouthbrooders, meaning that after spawning, an adult female will pick up her eggs and deposit them in her mouth for a period of time to allow for development before releasing fully-formed fry. Because of their life cycle, it is extremely important to quarantine new fish prior to introducing them into your main tank.

The easiest way to do so is by purchasing a separate 20 gallon tank (breeding tanks should be bare-bottom with no plants), filling it with water from your existing aquarium, and adding only a conditioner, if necessary, to reduce chlorine levels.

When you have acquired at least one male and one female specimen from reputable sources, fill half of the breeding tank with water from your existing aquarium; then add both corys slowly over about five minutes. The sudden change in pressure will cause them to release any brood they may already be carrying, which you can scoop out and return to your established tank once they’ve adapted to their new environment.

Once they’re separated, add three or four sinking pellets and place some broad-leaf plant matter—such as melaleuca—in the tank so they can easily find food while they adjust.

Are Corydoras Similis aggressive or peaceful?

If you’re keeping it with non-carnivorous fish like hatchetfish or gouramis, then you won’t have a problem. However, if you keep them with other catfish that do require meaty foods, then they can become territorial and end up turning on their tank mates. They are generally peaceful though, so if your tank is big enough to keep them away from all other fish, then there should be no issue.

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Corydoras Similis care

Corydoras similis

Your goal should be to keep the water clean and stable at all times. Adding some plants will also help oxygenate your water, which is important for all aquarium inhabitants. The best way to achieve that balance is by doing regular water changes and keeping some kind of biological filtration in place. A simple hang-on-back filter with a foam block or ceramic media would be a good choice for an aquarium with only one fish species.

In general, more complex filters are not needed and can cause more harm than good in smaller tanks. However, if you have multiple species or very picky eaters, you may need a more advanced filter like protein skimmers or wet/dry filters, just make sure they are sized properly for your tank!

Corydoras Similis diet

The smudge spot cory eats algae and other detritus. They will also eat meaty foods such as bloodworms, brine shrimp, tubifex worms, or freeze-dried daphnia. Use frozen bloodworms to treat ick because they have a high-fat content and are rich in iron to help replenish red blood cells that may be damaged by ick treatments.

Water parameters

Corydoras similis

Ideal water conditions should be a temperature of 20-26°C (68-78°F), pH of 6.0 – 7.5; and hardness of 4 – 15 dGH, Brackish with very strong water flow. Like other related species such as Corydoras julii and Corydoras aeneus, they are herbivores and need vegetable matter in their diet.

It is often recommended to use algae wafers, but there are a number of commercial foods that can be used instead, or alongside tablets or powder made for catfish and ornamental fish that make good substitutes. They should be fed once or twice a day depending on how much food is available at any given time as they have small stomachs.

Corydoras Similis lifespan

They can live up to 5 years in captivity (or more with good care and conditions)

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Parasites and diseases

Despite how easy these fish are to care for, they are sometimes affected by parasites and disease, just like most other aquarium fish. Fortunately, these types of issues can be treated easily with medications; without proper treatment, diseases and parasites can quickly spread to a tank’s other inhabitants.

You will want to make sure that your tank is cycled before you introduce any fish. The smudge spot cories are subject to several parasites and diseases, including infections with protozoa, flukes, and worms such as nematodes. Other potential ailments include bacterial infections, fungal infections, and mouth rot. Watch for symptoms of infection—such as swelling or reddening on the skin—and keep your tank clean to help prevent disease.

If your pet has a medical issue, contact your local veterinarian or an experienced hobbyist who is familiar with treating tropical fish.


As small fish, Smudge Spot Cories are preyed upon by a number of different predators including larger fish, birds, and even other Cories. They are one of several small species that spend most of their time hiding among plants or near driftwood rather than swimming around in open water.

Piscivorous fish, crayfish, and crabs are their main predators. The smaller ones are more prone to predation than the larger ones.

Do Corydoras Similis make good pets?

Yes. They are hardy and can survive in most water conditions, making them a perfect addition to your display tanks.