How Many Corydoras Should Be Kept Together? The Perfect Group Size for Happy & Healthy Fish

With dozens of popular species to choose from, Corydoras catfish—nicknamed cory catfish or cories—make perfect additions to freshwater community tanks. These active little bottom-dwellers are peaceful by nature but not lacking in personality. Plus, they come in a wide range of colors and patterns to help you customize your aquarium down to the finest detail.

The key to keeping Corydoras happy and healthy is to stock them in groups. Here’s what you need to know about popular cory catfish species and how many Corydoras should be kept together.

Corydoras Basics

The name Corydoras applies to a genus of freshwater catfish that contains over 160 unique species. While there are dozens of Corydoras species, the distribution of the entire genus is limited to South America. In fact, many cory catfish species are endemic to a restricted area within the larger distribution range.

Like other catfish, Corydoras have bony plates of armor rather than scales. They come in a diverse array of body shapes, colors, and patterns but generally remain small. Most cories reach a maximum size under three inches, though several top out at just 1 inch in length. 

Some of the most popular Corydoras species in the aquarium trade include the following:

  • Bronze Cory (Corydoras aeneus) – Also known as the green cory, bronze cories are blue-gray in color over the head and back with yellow or pink bodies. They grow up to about 2.5 inches in length.
  • Albino Cory (Corydoras aeneus) – The albino cory is simply a color variant of the bronze Corydoras, easily identified by its all-over pink or white coloration.
  • Panda Cory (Corydoras panda) – A little smaller than the previous two cories, the panda cory grows up to 2 inches long and can be identified by the black spots over the eye, on the dorsal fin, and in front of the tail.
  • Peppered Cory (Corydoras paleatus) – Perhaps one of the most widely available species, peppered cories are named for their pattern of dark and light splotches.
  • Sterbai Cory (Corydoras sterbai) – This striking species is easily identified by its polka-dotted pattern on the body and fins. Some even have a noticeable orange color on the smaller fins.
  • Pygmy Cory (Corydoras pygmaeus) – Growing up to 1 inch in length, the pygmy cory is popular for nano tanks. These cories have silver-gray bodies with a black line running horizontally from nose to tail.

As is standard in the aquarium trade, Corydoras have been subject to commercial cultivation and selective breeding. Captive breeding has made some of the rarer species more readily available and has also resulted in some unique color variants.

The Gold Laser Corydoras, for example, is known for the vivid orange stripe that runs down its back. The Black Venezuelan Cory, a variant developed by German aquarists, stands out with its all-over black and dark maroon coloration. The Orange Venezuelan Cory is blue-gray in color but develops a bright reddish-brown color as the species matures.

Discover how many corydoras should be kept together.

Cultivating a Corydoras Tank

Most of the Corydoras catfish available in the aquarium trade are tank-bred, so they are generally hardy and adaptable to various tank conditions. That said, cories are most likely to thrive when kept in a tank that simulates their native habitat. This means fairly warm temperatures and soft, slightly acidic to neutral water.

Here’s a quick overview of the ideal water parameters for Corydoras:

  • Temperature: 70°F - 78°F
  • pH Range: 5.5 – 7.5
  • Water Hardness: 2 – 15 dGH

Tank size is important for Corydoras catfish, especially considering their need to be kept in schools. A minimum of 20 gallons is recommended for a small group of cories. Because Corydoras are bottom-dwellers, you can keep them with mid- and top-dwelling species as long as you don’t overstock the tank.

Planted tanks are ideal for Corydoras, not only because plants help mimic their native habitat but the plants keep the tank oxygenated. Cories prefer soft, fine substrate like sand or aqua soil they can dig through without injuring their fragile barbels. Be sure to provide plenty of caves and places to hide as well, since Corydoras are nocturnal and will generally hide during the day and become active in the evening.

Many Corydoras species are found in slow-moving streams, so it’s not necessary to create a strong current in your tank. Maintaining high water quality is a must, however, so install an adequate filtration system and perform routine water changes as needed.

Ideal Corydoras Group Size

In a well-maintained tank, all Corydoras need to thrive is a healthy diet and a group of their own kind to shoal with. Wild Corydoras are known to live in groups of 20 or more, so there’s really no risk of stocking too many cories in your tank—as long as it’s big enough to accommodate them all. At a minimum, keep at least six of the same Corydoras species in your tank.

Keeping your Corydoras in groups will help your fish feel more comfortable in their environment. When your fish are comfortable and confident, you’ll get to enjoy the full range of their unique personalities and active behaviors. When the lights go out at night, you may even see your cories exploring the middle and upper levels of the tank or darting to the surface for a quick breath of air.

Corydoras Breeding Tips

Another benefit to keeping Corydoras is groups is that it makes breeding more likely. Many Corydoras species reproduce readily in home aquariums when conditions are kept stable. If you want to encourage spawning, try performing a large water change and make the water you refill the tank with just a few degrees cooler. This helps simulate the rainy season during which Corydoras naturally breed in the wild.

To increase the odds of Corydoras eggs hatching and growing to maturity, provide plenty of cover at the bottom of your tank. Adult Corydoras will deposit their eggs on flat surfaces like decorationsplant leaves, or even the walls of the tank.

Corydoras don’t exhibit any parental care and are prone to eating their own eggs and fry, so offer a dense mass of guppy grass or java fern to give the fry cover. You can also carefully remove the eggs to a separate rearing tank and raise the fry on baby brine shrimp and powdered fry food when they hatch.

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