About Cory Catfish
If you’re interested in Cory Catfish, you’ve come to the right place. Cory Catfish – also known as Corydoras or Cory Cats – are a type of freshwater fish native to gently flowing streams and rivers of South America, where they can generally be found foraging for food along the river bed.
Cory Catfish are really hardy and easy to care for, which makes them a great fish for beginners and has helped to established their position as one of the most popular aquarium species in the world today.
In this article, we’ll teach you everything you need to know about Cory Catfish – from setting up your tank to providing the right food and water conditions, keeping your Cory Catfish with suitable tank mates, spotting and treating potential health problems, and even breeding the next generation of Cory Cats!
How many types of Cory Catfish are there?
There are at least 165 Cory Catfish types.
10 of the most popular types of Cory Catfish are:
- Three Stripe
You can read about some of the most popular, and find a list of all 165 species, here.
While you should properly research your choice of Cory Cat species before buying them, most species have similar needs in terms of tank setup, water conditions, tank mates, food and substrate.
How big do Cory Catfish get?
The size of your Cory Catfish will depend on their species, but all types of Cory Catfish are between 1 inch and 5 inches long.
As the name suggests, the smallest species of Corydoras Catfish is the Pygmy Cory. Females are often around 1 inch long and males are even shorter at around 0.75 inches.
The biggest species of Corydoras Catfish is the Banded Cory. Banded Cory Cats can grow to be over 4 inches long.
The final size of your Cory Cats will be determined by genetics (species and breeding), as well as by their tank size and conditions, water temperature, diet and amount of food, and the number of other fish in the same tank. Well-fed Cories kept in warmer water with the right parameters and plenty of space will grow more quickly and to a larger size, though their maximum size will always be limited by their genes.
How fast do Cory Catfish grow?
Cory Catfish hatch from their eggs as very small tadpole-like creatures measuring just a few millimetres long. Within 9 to 12 months, they will grow to around 2 inches long, which is full adult size for some species.
Larger Cory Catfish may keep growing beyond 12 months old, though their rate of growth usually slows down as they get older, eventually stopping entirely.
How long do Cory Catfish live?
Given the right care, Cory Catfish live for 5 to 10 years. If your Cory is over 5 years old then you can be sure that you’re doing a good job of looking after them, but they may still have a lot of life left in them yet!
As with all animals, genetics plays an important role in determining how long an individual Cory Catfish will live. There’s nothing you can do to change this, so if you have a fish that dies at a young age, it isn’t necessarily your fault. However, if your Cory Cats consistently die aged less than 5 years, you may want to look at your setup and care routine to see if there’s anything you can do to extend their lifespan.
Tank setup for Cory Catfish
We’ve learnt that Cory Catfish can live for 5 to 10 years with the proper care, but what tank conditions do they need in order to live a long healthy life?
Read on for our Corydoras Tank Setup Q&A where you’ll discover the ideal tank size and conditions for your Cory Cats.
How many Cory Catfish should be kept together?
Cory Catfish are schooling fish, which means they naturally live in groups with fish of the same species. While it is possible for a single Cory Catfish to live alone, this goes against all of the fish’s natural instincts and it would be unlikely to stay healthy or happy for long.
You should keep Cory Catfish in groups of at least 5 individuals (preferably more) in order for them to form a school and swim around the tank as a group.
Keeping your Cory Catfish in a school of five or more fish will not only keep them healthy and stop them from getting stressed, it will also allow them to exhibit schooling behavior. A group of Cory Catfish swimming around the bottom of your tank in formation is a beautiful sight and one that you’ll miss out on – or not enjoy to its full effect – if you keep less than 5 fish.
What size tank do Cory Catfish need?
The absolute minimum tank size for Corydoras Catfish is 10 gallons. Cory Catfish are schooling fish that should be kept in groups of five or more – a 10 gallon tank is therefore allowing at most 2 gallons of water per fish. And that’s before you allow for space lost to your filter, substrate, plants and decorations. While it is possible to keep Cories in a tank of this size, it’s far from ideal.
It’s always best to buy the largest tank you can afford and have space for. If at all possible, we recommend setting up a 20 gallon tank (or larger) for Cory Catfish.
If you do need to choose a smaller tank then consider buying a smaller species of Cory. Pygmy Corydoras grow to just 1 inch long, which makes it possible to keep your group of 5 or more in a smaller tank than would be needed for larger species.
All of our advice assumes that the Cory Catfish are the only fish in your tank. If you are keeping tank mates along with your Cories then you will need to increase your tank size accordingly.
You should always choose a long tank with a large surface area for Cory Catfish rather than a tall tank. This is because they are bottom-dwellers that enjoy exploring the bottom of the aquarium. A long and wide tank will give them a larger area to explore than a tall, deep tank of the same volume.
How many Cory Catfish can you keep in a 10 gallon tank?
If you only have a 10 gallon tank then we recommend keeping 5 Pygmy Corydoras.
Pygmy Corydoras are the smallest Cory species, so it is possible to keep 5 individuals in a 10 gallon tank while still allowing 2 gallons of water per fish.
If you would like to keep more Cories, or larger species, then a 10 gallon tank is not suitable and you will need to buy a larger tank or reconsider your options.
We strongly advise against keeping a smaller number (less than 5) Cory Cats in your 10 gallon aquarium. Corydoras are schooling fish and should always be kept in a group of 5 or more.
How many Cory Catfish in a 20 gallon tank?
We recommend keeping up to 10 Cory Catfish in a 20 gallon tank. This could be 10 of the same species or perhaps two different species in groups of 5.
For a 20 gallon tank, you could choose a species that grows to a maximum size of 2 to 2.5 inches, such as Bronze Corydoras.
Avoid keeping larger species – such as Banded Corydoras – in a 20 gallon tank as you will not have enough room to keep a school of enough individuals.
What kind of substrate is good for Cory Catfish?
Sand is the best substrate for Cory Catfish. Cory Cats spend their waking hours wandering the bottom of the aquarium sifting through the substrate in search of food. Sand allows them to do this without injuring themselves.
If you choose gravel as a substrate then your Cory Cats won’t be able to sift through it as easily and may injure themselves trying.
In the wild, Cory Catfish live in rivers and streams with muddy or sandy beds. It’s this kind of environment that you should try to recreate in the home aquarium in order to keep your Cory Cats healthy and engaged.
What pH do Cory Catfish need?
Cory Catfish are not particularly sensitive to pH. They will happily live in water with a pH anywhere between 6.0 and 8.0.
Even if your pH falls slightly outside this range, we would not recommend trying to adjust it unless you notice problems with your fish and have good reason to suspect that pH is the cause.
What temperature do Cory Catfish like?
Cory Catfish will be happiest in a water temperature between 72°F and 78°F (Approximately 22°C to 26°C) but can tolerate temperatures outside this range.
If the fish seem comfortable then we would not have any concerns about keeping Cory Cats in water between 70°F and 80°F (approximately 21°C to 27°C).
Feeding Cory Catfish
Like all pets, an essential part of caring for Cory Catfish is giving them a nutritious, varied diet and feeding them the right amount of food.
Keep reading for our Corydoras Food Q&A where we tell you everything you need to know to create the ideal healthy menu for your Cory Cats.
What do Cory Catfish eat?
Cory Catfish are omnivores (so they’ll eat foods originating from either plants or animals) and it’s fair to say they’re not picky eaters! Cory Cats will eat pretty much anything that is small enough to fit in their mouths.
While Cory Catfish can learn to come to the surface for food, their natural behavior is to search the bottom of the tank for scraps or plant or animal matter to eat. This makes them excellent tank cleaners – particularly in community tanks. Any food that other fish fail to eat will drift down to the bottom of the aquarium where it will be gobbled up by the Cory Catfish rather than being left to rot.
Fantastic foods to feed your Cory Catfish include bottom-feeder tablets, sinking algae wafers, shrimp pellets and freeze-dried bloodworms. Just remember to feed your fish a variety of foods, rather than always giving them the same thing, as this ensures a varied diet containing a range of vitamins and minerals.
How much to feed Cory Catfish
A good rule of thumb is to feed your Cory Catfish as much as they can eat in five minutes. In most cases, this will work out to one pellet or a pinch of fish flakes for every two Cory Catfish.
How often to feed Cory Catfish
It’s important to remember that Cory Catfish love to scavenge food off the bottom of the aquarium and some food from every feed will always be missed and end up at the bottom of your tank. We therefore recommend feeding your Cories just once per day and leaving them to find leftovers for themselves the rest of the time.
Feed your Cory Catfish once in the morning. They will then spend the rest of the day happily searching for leftovers at the bottom of the tank.
How to make homemade fish food for Cory Catfish
Cory Catfish are not picky about what they eat so it’s very easy to produce ‘homemade’ foods for them to supplement their diet of pellets, flakes and other fish foods.
As long as the pieces are small enough, Cory Catfish will happily eat small pieces of blanched vegetables or hard boiled egg yolk that has been dried and then sprinkled into the tank in small pieces.
Cory Catfish Tank Mates
Cory Catfish don’t have to be kept exclusively with their own species. They make fantastic community fish and will quite happily share a tank with many other fish species.
If you have a large enough tank then keeping Cory Catfish in a community tank can work extremely well. The Cory Cats will add interest at the bottom of the tank, as they explore the substrate in a small group looking for food, while the other fish will swim around in the middle of the tank or closer to the surface.
However – while Cory Cats are fantastic community fish – they do of course need to be kept with peaceful species that share similar needs, including enjoying the same water temperature. You also need to make sure that you have a large enough tank for all the fish you want to keep.
What fish can live with Cory Catfish?
To live with Cory Catfish, the potential tank mate needs to be a freshwater species that enjoys a tank temperature of 70°F and 80°F (approximately 21°C to 27°C), is peaceful and won’t bother your Cory Cats or try to eat them, and is small enough that you’ll have enough tank space.
Examples of fish that can live with Cory Catfish include:
All of these species will happily live alongside adult Corydoras. Our only note of caution is that some of the above (such as guppies) will eat – or attempt to eat – newborn and juvenile Cory Cats. We therefore recommend keeping tank mates along with your Cory Catfish in adult tanks only. If you plan to breed your Cory Cats then it is probably best to give them their own tank – or be extra careful about which tank mates you choose – rather than attempting to breed them and raise their fry with other fish around.
Breeding Cory Catfish
Cory Catfish are very easy to breed without any specialist skill, so even if you’re a beginner fish-keeper, it’s likely that your Cory Cat family will soon grow beyond the number you bring home from the pet store.
Of course, the most important thing if you’re going to breed Cory Catfish is to have a suitable home for the newborn fry. This could be in a separate tank or in one tank along with the adults as long as you have enough space.
How to tell the sex of a Cory Catfish
It’s fairly easy to tell the difference between male and female Cory Catfish – at least by fish standards, where accurately determining sex can often be very challenging.
The best way to tell the difference between a male and a female Cory Catfish is to view them from above. Female Cory Catfish will be larger and fatter than males. Male fish will be noticeably smaller and generally look much more slender.
How to breed Cory Catfish
There are two ways to breed Cory Catfish: The ‘natural’ way is to leave your Cory Cats in together in a mixed group of males and females and let nature take its course. The more proactive way is to set up a separate breeding tank and transfer selected adult fish into that tank to breed.
The natural method
If you don’t mind which males and females breed – and your tank does not contain other fish that will eat Cory eggs and fry (babies) – then the natural method may work best for you. You may find that your Cory Cats breed on their own without any intervention from you. If not, you will need to lower the temperature of your tank water by slowly adding cool treated tap water.
To get Cory Catfish to breed, add cool water to your tank until the tank temperature is approximately 65°F (18-19°C).
The Breeding Tank Method
If you want to breed specific males with specific females or your main tank contains fish, such as guppies, that will eat Corydoras eggs and fry, then you’ll need to set up a breeding tank in order to safely breed your Cory Cats.
The first step is to set up a breeding tank (10 gallons +), consisting of a filter, air pump and air stone, and ideally a heater. Keep the bottom of the tank bare – there’s no need to add gravel, sand or any other substrate. The water in the tank should match the water in your main tank in terms of pH, temperature, etc.
Next, transfer a trio of adult Corydoras into the breeding tank. The trio should consist of one male and two females.
Let them get used to their new surroundings for three days, then start slowly adding cool treated tap water to the breeding tank.
Soon after the water temperature gets down to around 65°F you should notice small eggs stuck to the tank base and walls. It’s now time to return the adult fish to the main tank.
Turn on your air pump and add some methylene blue to the breeding tank. This will help prevent fungus from infecting the eggs before they hatch.
Over the course of the next day or so, steadily raise the breeding tank temperature to around 72°F (22°C).
Within a week, you should start to see baby Cory Catfish hatching from the eggs!
How to tell if a Cory Catfish is pregnant
Cory Catfish don’t get pregnant. Only ‘livebearers’ – fish that give birth to free-swimming young – get pregnant. Cory Catfish lay eggs.
If you think one of your Cory Catfish looks pregnant then it is likely a female fish that is carrying eggs.
What do Cory Catfish eggs look like?
Cory Catfish eggs look like small beige balls with a dot in the middle. They stick to all kinds of surfaces around the tank. You can see an example of Cory eggs in this Reddit post.
How to know if Cory Catfish eggs are fertilized
Fertilized Cory Catfish eggs are beige with a dark spot in the middle. Infertile eggs are white and translucent.
How often do Cory Catfish lay eggs?
How often Cory Catfish lay eggs will depend on your water conditions and the number of Cories you have in your tank. However, it’s possible for a female Cory to lay eggs as frequently as once per week given the ideal conditions.
How many eggs do Cory Catfish lay?
Cory Catfish lay a lot of eggs at one time. The exact number varies from fish to fish and from spawning to spawning, but the number of eggs will generally be somewhere between 50 and 150 eggs.
How long does it take for Cory Catfish eggs to hatch?
Cory Catfish eggs usually hatch within 3 to 6 days. Only fertilized eggs will hatch and it is important to keep the eggs free from fungus until they hatch.
You should use methylene blue to help prevent fungus and remove any eggs that are infected with fungus from your tank. You should also remove unfertilized (white, translucent) eggs too.
How to prevent fungus on Cory Catfish eggs
If you notice a hairy or algae-like substance on your Cory eggs then they are infected with fungus. These eggs should be removed from your tank immediately before other eggs become infected.
To prevent fungus on Cory Catfish eggs you should always use an air pump in your tank to ensure plenty of water movement and treat the water with methylene blue.
What to do with baby Cory Catfish
To give your baby Cory Catfish the best chance of survival, it’s best to move them into their own tank, if they’re not in a breeding tank already.
While it’s certainly possible for baby Cory Catfish to be born in the same tank as the adults and grow to adulthood, there are a lot of dangers, such as getting sucked into the filter or being eaten by other fish. A tank of their own means you can setup the right conditions to keep them safe.
As baby Corydoras are only small, your fry tank can be small too. However, it should still have the right water parameters (temperature of 72°F / 22°C, no ammonia or nitrite, etc) and you will need to do regular water changes of up to 10% of the tank water.
It’s best to use a sponge filter in a baby Cory Catfish tank, as this removes the possibility of the fry getting sucked into a box filter or external filter inlet.
What to feed newborn Cory Catfish
For the first few days of their lives, newborn Cory Catfish will be attached to a yolk sack, which contains all the food they need.
After a few days, the yolk sack will be absorbed and you’ll need to start feeding them. Good food options for newborn Cory Catfish include crushed shrimp pellets, Hikari First Bites, and microworms.
Sick Cory Catfish
When you see your Cory Catfish acting strangely or notice unusual marks on the fish’s body then it’s almost certainly a sign of disease, stress or some other problem. It’s important to get to know what your fish usually look like and how they behave so you can spot problems and take action at the earliest opportunity.
Why is my Cory Catfish laying on its side?
If your Cory Catfish is laying on its side or swimming upside down then it has a problem with its swim bladder. The swim bladder is an organ that helps your fish to maintain its balance and buoyancy in the water – like a balloon that fills and deflates as needed.
Swim bladder problems can be caused by all kinds of things, from overeating to bacterial infections or even stress. Unfortunately, this can make it very difficult to find the cause of the problem.
If your Cory Catfish is laying on its side then we recommend checking:
- Water temperature: Is it outside of the range 70°F to 80°F (21°C to 27°C)?
- pH: Is it outside of the range 6.0 to 8.0?
- Ammonia: Is it above zero?
- Nitrite: Is it above zero?
- Nitrate:Is it above 40ppm?
If all of these parameters are where they should be then you should consider your fish’s environment next. Do they have enough tank mates (you should always keep Cory Cats in groups of 5, preferably more), enough floor area to explore at the bottom of the tank, and enough plants (whether real or fake) to explore and hide behind? If not, try adding more of these, as it may help your fish feel more comfortable and prevent them from getting stressed.
Next, think about how much you’re feeding your fish. Overeating can cause swim bladder problems, so not feeding your fish for a few days could be the answer. Don’t worry – they won’t starve!
If all of your water parameters are ok, you’re feeding your fish properly, you have plenty of Corydoras to form a school, lots of plants and the right tank setup, then the next thing to consider is infection. At this point, it’s best to remove the sick fish from your tank and place them in a quarantine tank where they can be treated.
Treatment for swim bladder problems can include:
- Not feeding the fish for a few days
- Using a shallow amount of water and keeping the water quite still, as this will help your fish to control its swimming more easily
- Raising the water temperature to between 78°F and 80°F (26°C to 27°C)
- Adding a small amount of aquarium salt to your quarantine tank
- Feeding peas (in small amounts, just one at a time) with the shells removed
Treatment is not always successful and unfortunately swim bladder problems are often fatal. However, if you take the steps above, you’ll give your fish the best chance of survival.
Why is my Cory Catfish swimming at the top of the tank
If you see your Cory Catfish swimming near the top of the tank then it could be a sign of low oxygen levels in your tank water. This could be caused by high temperatures, by a lack of movement at the surface of the water, or by overcrowding.
To get more oxygen into your aquarium water, add cool treated tap water during water changes to lower the water temperature. Lower the temperature of your heater if you have one and, if necessary, consider moving your aquarium to a cooler location in your home. This will help as cool water holds more oxygen than warm water.
You should also make sure that there is plenty of movement on the surface of the water. Is your filter causing your water to flow around the tank? Is your air pump causing bubbles and ripples at the surface? This surface movement is a good thing, as it helps oxygen from the air dissolve into the water.
If your tank water is too still and stagnant, try adding an air pump, increasing the air flow or adjusting the flow from your filter.
Featured image credit: iStock.com/Mirko_Rosenau