Eric is an aquarium enthusiast with over two decades of experience caring for a wide array of tropical fish.
The Corydoras Catfish
The cory (corydoras) catfish is one of the most popular aquarium fish in the world. With their stubby little bodies and mustache-like whiskers, they are also downright adorable. They putter around the bottom of the tank looking for bits of uneaten fish flakes or other forgotten edibles. Cories are a lot of fun to watch, but they also perform an important role as part of the “cleanup crew” in your tank.
The cleanup crew consists of fish that help keep the tank neat and tidy. Some are algae eaters, where others, like the cory, help by finding and eating bits of food that fall to the substrate. This prevents the food from decaying and fouling the water. Your cleanup crew can’t do it all, but their efforts help with routine maintenance in your aquarium.
Cory catfish grow to an adult size of two to three inches, and they do best in shoals of six or more. There are a bunch of different varieties, some common in the aquarium trade and others more exotic.
They are among the best freshwater fish for beginners. Cories are peaceful fish, excellent for community aquariums, and very easy to care for. But, there are a few things you need to know if you intend to stock them.
This article will cover the basics of cory catfish care.
Cory Catfish Care Sheet
~ 2.5 inches
Minimum Tank Size
10 gallon; 30 preferred
Fish flakes, sinking pellets
Natural Habitat and Behavior
Wild cories come from South America where they inhabit slow-moving creeks and streams and shallow, calm water on the edges of rivers and ponds. Dense vegetation provides not only an ideal habitat for the corydoras to find food but also cover from predators.
They are shoaling fish, meaning they live amongst a large group of others of their same species. Wild cories forage for tiny insects, larvae, and worms and stick to the river or pond bottom to do their hunting. They are most active during the day.
Cory catfish possess a labyrinth organ, which means they can shoot up from the bottom and gulp air from the surface when necessary. In the wild, this helps them to survive brief periods in a low-oxygen environment.
Cories in the Home Aquarium
Cories can live in a tank as small as 10 gallons, but I recommend at least 30 gallons. That’s because, just like in the wild, cories are best kept in small schools in the home aquarium. This means a minimum of six individuals, but more is better if there is room in the tank.
You will see them group together, especially at night when they seek security, but remember they are shoaling fish, not schooling fish. They don't often pack tightly and move together in schools. Most home aquariums are small enough that no matter where they are in the tank they are always relatively close together.
Plants and Decorations
Live plants are a great addition to their tank, as they give your cories a place to hide and mimic their natural environment. If possible, you may wish to replicate their wild regional habitat by including plants that come from their same native area. You may include plants such as the Amazon sword along with natural river rock and driftwood.
If live plants aren’t possible, artificial plants and decorations will do. Remember, while cores do their best to reach every nook and cranny of your aquarium, they can’t get everywhere. You may wish to avoid decorations with crevices that will trap food your fish can’t reach.
Busy little cories search tirelessly for every bit of food that slips past the fish who live above them in the water column. They will find and munch up most of the lost fish flakes.
This may or may not be enough food for your cories to thrive. To make sure they are getting enough to eat, include sinking pellets with each feeding. Sinking pellets will fall to the bottom of your tank while the other fish are devouring the fish flakes and give your cories a head start on getting some grub.
Cories are among the most peaceful freshwater aquarium fish. They mind their own business, doing their daily work, and they pose no threat to any other fish in your tank. They are not territorial or aggressive and this makes them outstanding fish for a community tank.
Types of Cory Catfish
You will find many types of cories available for your tropical aquarium. Here some of the more common:
- Pepper Cory
- Albino Cory
- Bumblebee Cory
- Bronze Cory
- Panda Cory
- Sterba’s Cory
- False Julii Cory
- Pygmy Cory
- Skunk Cory
Also be aware of one more type of “cory” you will see, the emerald green cory or emerald brochis. They grow larger than true cories as adults, reaching a total length of around four inches.
Ideal Water Parameters
7.0 - 8.0
Best Cory Catfish Tank Mates
Since they are such peaceful community fish, the cory catfish is suitable for almost any tropical aquarium inhabited by other community-appropriate fish. They can also do well in tanks with semi-aggressive inhabitants, as most fish will ignore them.
As always, be sure to research any fish you intend to stock so you know they are compatible with your cories. Here are a few suggestions that come from the same general area of the world as the corydoras.
Freshwater angels are beautiful South American cichlids. In the wild, they are found in many of the same areas as the corydoras. Angels are large fish, and if you have a tank big enough to house them, you also have the space for a school of cories.
The common Plecostomus is one of the most prolific algae eaters in the aquarium world. That means it can be part of your tank cleanup crew, just like the cory. Unfortunately, the common pleco grows to an adult length of nearly two feet, and that makes it inappropriate for most home aquariums. Instead, look for the rubbernose and bristlenose pleco, which only grow to around five to eight inches.
Plecos are notoriously hard on live plants, so if you wish to have a planted aquarium you may want to give them a pass altogether. But, if you still want an algae-eater for your cleanup crew, you can look to the little otocinclus catfish. Otos grow to around two inches, and like cories, they need to be kept in groups of six or more.
No Amazon biotope tank would be complete without neon tetras. I love the look of a large school of neons in a planted tank. They are peaceful community fish, but because they are very small, you will want to be careful which other fish you stock with them. For example, they may not be the best choice to keep with large angelfish.
The silver dollar is a relative of the piranha, but don’t worry. These guys are peaceful, and, while they might munch up a plant or two, they typically don’t bother other fish. They are large, schooling fish, though, so they are only appropriate for tanks 150 gallons or larger.
Corydoras Catfish FAQ
Here are some frequently asked questions about the cory catfish:
How big do cory catfish get?
Cories reach an adult length of about 2.5 inches.
Do cory catfish really clean the tank?
They sure try their best. If there is edible food or debris they can get to, they will hoover it up. However, they can’t always reach every crack or crevice in plants or decorations. As with any cleanup crew fish, they can help, but you’ll still need to roll up your sleeves and perform proper scheduled tank maintenance.
How many cory catfish should be kept together?
Cories are shoaling fish, so the more the merrier, without overstocking your tank, of course. At a minimum, you’ll want a school of at least six of each type of cory you stock. You can have many more in large tanks. In a very large tank, you may have schools of several species of cory.
How many cory catfish in the 10-gallon tank?
I’d suggest six cories in a ten-gallon tank would be fine if you stock no other fish. If you wish to have more fish, you will need a bigger tank if you wish to have cories. When shoaling fish aren’t kept in large enough schools, they can become stressed and prone to illness.
What size tank do cories need?
If you intend to have a community tank with several other types of fish, you’ll want at least a 30-gallon tank for a school of cories. Larger tanks are also better for growing live plants.
Why do cories swim to the surface?
They occasionally come to the surface to take gulps of air. This is normal behavior and nothing to worry about. However, if you notice your cories constantly coming to the water surface for oxygen, it could be a sign of poor water conditions.
As you can see, the cory catfish is one of the easiest fish to keep if you follow a few simple rules:
- Keep in them in a school of six or more in a large enough tank.
- Feed sinking pellets so they get enough to eat.
- Keep up with tank maintenance and don’t expect your cories to clean the tank for you.
They are also among the most fun fish to watch. These little catfish always seem to be up to something, and because they are active in the daytime, we get a front-row seat. It is no wonder these fish are among the most popular in the aquarium industry.
As with any fish you intend to stock, be sure to do as much research on the cory that you can before you bring them home. Good luck!
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2021 Eric Dockett