The Cory Catfish is one of the most famous bottom dwellers that you can keep in a freshwater aquarium.
They are famed for their small size and beginner friendliness.
With over 100 different species available, each one is just a little different from the other. They each have their own color, pattern and personality. However, there are a few universal traits that all Corys share.
All of them are quite easy to care for and they all get along very well with other tropical fish.
Keep reading for a complete and comprehensive guide to caring for any Cory…
Table of Contents
- Cory Catfish Overview
- Cory Catfish Appearance
- Habitat and Tank Conditions
- Cory Catfish Tank Mates
- Cory Catfish Care Guide
- Breeding Cory Catfish
- History and First Sighting
- Should You Keep Cory Catfish? (Summary)
Cory Catfish Overview
Corydoras Catfish are small freshwater Catfish that belong to the Callichthyidae family.
These little Catfish are native to Central and South America and are best known as algae eaters.
You can find over 170 types of Corys with the most popular being the Peppered Cory (Corydoras paleatus). Their brown body is covered in deep blue spots which shine in green or blue tints when the light hits them.
Since they are scattered all over Central and South America they have adapted to many different habitats.
Some Corys have a higher tolerance for acidity and transient water parameters, while others may prefer a more stable environment.
There are some species that produce toxins and others even carry venom in small spines on their fins!
Get to know each species thoroughly before you commit to one and remember that some species are more beginner friendly than others.
The most common species cost about $5-$10, with more exotic varieties going for $25-$100.
Do Cory Catfish Clean The Tank?
Cory Catfish have received a reputation as being live-in janitors and algae eaters.
However, they are not particularly good at this job.
In the wild Algae is only a very small part of their diet.
They do not seek it out intentionally but will eat it if it is the only thing they can find in the tank.
Corys much prefer worms, water fleas and other micro prey. Sometimes they will take in algae while grazing in the substrate for their favorite foods.
While they may not be the best at cleaning the tank, they do make pretty good pest control fish. They will eat any nuisance worms or bugs that they find crawling around in the substrate.
You should read our article on the best algae cleaners if you are looking for live-in janitors.
- Experience Required: Beginner to intermediate.
- Nicknames: Corydoras, Cory Cat.
- Color Forms: Species dependent.
- Size: 1-4 inches.
- Tank Size: Minimum 10+ gallon.
- Tank Temperature: 71°F-82°F.
- Many different varieties to choose from
- Friendly to their own kind
- Can clean small amounts of tank waste
- Compatible with lots of tanks
- Not an efficient algae cleaner
- Some species are poisonous
- Sensitive to shifting parameters
- Tank needs frequent cleaning
Cory Catfish Appearance
Each variety of Cory Catfish has their own distinctive appearance.
However there are a few traits that are true across the board.
Instead of scales these Catfish are covered in thick armor plates that protect them from predators and other hazards.
Also, just like many other Catfish, their snouts are flanked with short barbels. These sensory organs are used to detect movement and pressure changes at the bottom.
They have a triangular shaped head, sloping forehead and a plump little body.
The smallest species are only 1 inch long, while others can grow all the way up to 4 inches. Some species are solid colored, while others can be spotted or striped. Many popular varieties have shimmering iridescent scales.
Cory Catfish have 7 small transparent fins.
There is a primary dorsal fin on the head, and a very tiny secondary dorsal fin set near the tail.
There is also a pair of pectoral fins, a pelvic fin and an anal fin set right at the base of the caudal fin.
The pectoral and dorsal fins have sharp spines (which can sometimes contain venom).
Types of Cory Catfish
Corydoras is the most diverse genus of freshwater Catfish.
Currently there are 174 known species.
While not all of these species are available for aquariums there are still plenty that are. Here are the most popular types of Cory Catfish.
Peppered Cory Catfish
Corydoras paleatus is the most common Corydoras species to find.
At first glance they look like a simple brown colored Catfish with black pepper spots. However the real magic happens once the light hits them. When under the right light their scales sparkle in beautiful blue and green hues. Peppered Cory Catfish are one of the easiest to manage and make a great choice for beginners.
Green Cory Catfish
Green Cory Catfish are green version of Corydoras aeneus (the Bronze Cory).
This variety has a thick iridescent green line against a copper colored body.
The Green Cory is an excellent species for anybody who is looking to try out the Corydoras genus for the first time.
Albino Cory Catfish
This is an albino version of Corydoras aeneus (the Bronze Cory).
They are bred by pairing 2 Bronze Cories that carry a specific recessive gene.
The result is a stark white Catfish with a slightly pink tint, pink eyes, and glittering scales.
Unfortunately they are often afflicted with light sensitivity, vision impairment and even total blindness. They are also more susceptible to disease and harassment from tank mates. Because of this they need a peaceful low lit environment shaded by lots of plants.
Panda Cory Catfish
Panda Corys are one of the newer species and were discovered in the 1970s.
Their colors resemble a panda bear, which is how they got their name. They even have the same black markings over their eyes.
This species is native to Peru but the ones that you find in aquariums are usually bred in captivity.
Julii Cory Catfish
Corydoras julii is a Corydoras that resembles a Pleco. They are a tan brown color with thick black polka dots all over their body. The spots are thickest over the head and snout.
Juliis have very sharp spines on their pectoral fins, so being pricked by one can be quite painful!
Three Stripe Cory Catfish
The Three Stripe Cory looks very similar to the Julii. In fact they are often referred to as the False Julii.
While they look very similar there are a few ways to tell the two apart. The color is much lighter than that of the Julii and they have two long stripes on their ventral side instead of one short stripe.
Three Stripe are cheaper and more beginner friendly than Juliis too.
Habitat and Tank Conditions
Each variety of Cory lives in a slightly different habitat.
However there are a few universal requirements that all Corys need.
Cory Catfish prefer areas with fine grained substrate, low light and a moderate flow.
They are used to hypoxic environments with murky and slightly acidic conditions. Underwater plants are abundant in these areas (especially those that are adapted to low light).
You will need to keep the water temperature between 71-82°F and also keep it stable.
Depending on which species you have the pH can be anywhere from 5.5-7.5 and the hardness should range from 2-12 dGH.
While there is a very broad range of acceptable water parameters, it is important that they remain the stable at all times.
A good filter should be able to generate a moderate current and effectively remove ammonia, nitrates and other harmful waste products. Any filter that can simulate a rushing river will work (including an under gravel or waterfall filter). You can also try a bubble filter if you want to add extra oxygen to the tank.
Use soft sand as your substrate and layer it with smooth gravel. It is important that the substrate is soft enough to avoid injuring the fish.
You will need to use a low intensity light and keep the bottom of the tank heavily shaded. You should also place a lid on the tank for when your fish need to surface for air.
Logs, driftwood and bogwood all make excellent natural furniture for a Corydoras tank. There is no need to use anything that they would not find in their natural habitat.
Finally you will need to include plenty of plants.
The plants you choose must be able to handle a low light environment. Fortunately, there are plenty of low light aquarium plants that qualify.
- Amazon Sword Plants
- Brazilian Pennywort
- Dwarf Hairgrass
- Java Ferns
- Java Moss
- Micro Swords
|Minimum Tank Size||10 Gallons|
|Tank Type||Freshwater Planted|
What Size Aquarium Do They Need?
Some of the smaller Corys can live in a 10 gallon tank.
However most Corys will need to live in groups of 5-6 so they will need at least a 30 gallon aquarium.
You should add 5 more gallons of water for each one that you add beyond this number.
Cory Catfish Tank Mates
In the wild they often cohabitate with different species.
Because of this Cory Catfish are very peaceful and make excellent community fish.
Their size means thy can be kept with Nano fish.
The friendly Zebra Danio also makes a great tank mate.
Sparkling and Dwarf Gourami will also get along well.
Most of the popular live bearing fish will also make good tank mates including: Mollies, Platies, Swordtails and Cherry Barbs. Although you should avoid other Barb species.
Plenty of invertebrates can live in perfect harmony with this peaceful bottom dweller too. Nerite Snails, Mystery Snails, Amano Shrimp and Cherry Shrimp are just a few of the beneficial bottom dwellers that can clean up your Catfish’s tank.
In terms of incompatible tank mates, these include aggressive fish (Bettas, freshwater sharks, and any kind of Cichlid).
Large bottom dwellers such as Plecos and larger Catfish should also be avoided.
So should particularly boisterous fish like Tiger Barbs.
You should also avoid mixing venomous Cory species. Sterba’s Cory in particular can release toxins into the water which can poison other fish in your tank.
Keeping Cory Catfish Together
You should keep Cory Catfish in groups of at least 5 individuals.
The larger the group the more secure your Catfish will feel.
These fish are very social within their shoal and rely on group dynamics for security. You can spot them congregating in the same area of the tank, feeding together, or surfacing for air in groups.
Cory Catfish Care Guide
Each Cory species has slightly different care requirements and some are easier to keep than others.
The best beginner species include the Panda, Peppered, Bronze and Emerald Green varieties. Albino and Sterba’s Corys are among the few that first timers should avoid.
It is very important to keep the tank pristine with absolutely no traces of ammonia and other waste products. The tank must be cleaned once a week and fully cycled. Transient unsteady environments will cause a lot of stress which can be dangerous if the Cory releases toxins.
Red Spot Disease (or Epizootic Ulcerative Syndrome) is one of the most common diseases that affects this fish.
This fungal disease causes deep red ulcers on the fish’s body (particularly near the eyes). The ulcers can crack or bleed and may be covered in pus. Red Spot is easily treated with antifungal medication. Always be aware of any strange new markings that appear on your fish and isolate any fish that you think may be ill.
Also with Cory Catfish’s a thin body is a sign of illness, so you always want them to be a little on the chunky side.
Lots of keepers make the mistake of thinking this fish can survive on algae alone.
In the wild algae only makes up a very small part of their diet. Here they will snack on micro-worms, insect larvae and zooplankton in addition to algae and detritus.
When you spot them grazing at the bottom of the tank, they are looking for worms and tiny critters, not algae.
You will have to give it a similar diet to what it would eat in the wild.
There are special pellet foods that are made especially for bottom dwellers and these should be the primary part of your Catfish’s diet. In addition you can feed them quick sinking flakes and algae wafers.
Live foods include small worms, water fleas, and brine shrimp. Live or frozen insect larvae can be given as a treat.
A Cory Catfish’s diet is more limited than that of other Catfish, but they still eat plenty of different foods including:
- Bottom feeder pellets
- Fish flakes
- Algae wafers
- Brine shrimp
- Polychaete worms
- Insect larvae (treat)
- Plant material
You will only need to feed your Catfish once a day, and only enough food for them to finish eating in 5 minutes. If they are hungry for more they will snack on whatever they can find in your tank.
If you are looking for an active and entertaining fish then do not pick Cory Catfish!
They spends most of their time sleeping in the substrate.
During their active hours (just after sundown) you might catch them rearranging and moving your gravel in search of small prey.
However most of the time they remain at the bottom of the tank.
Every so often they will come to the surface to take in a mouthful of air. This is an adaptive behavior for fish from low-oxygen environments.
Corydoras will interact with similar sized fish and may even follow them if they do not have enough of their own kind to shoal with. This peaceful bottom dweller does not cause problems for other fish and most species are safe for beginner fish keepers.
Breeding Cory Catfish
Since these fish spend all of their time in groups it is fairly easy for them to breed.
To encourage your fish to breed you should keep them in groups with a female to male ratio of 4:2.
Your breeding tank should be at least 20 gallons and equipped with a sponge filter and air stone. The water temperature should be 75°F.
When courting the male will chase his chosen mate around the tank. Once he catches her he will climb on top of her to mate. The eggs are held between the female’s fins until they are fertilized. Once copulation ends the female will scatter the eggs in small clusters along the substrate.
Each cluster of 5 to 10 eggs will be laid in 10 minute intervals and it takes about an hour for the female to finish laying all of the eggs.
The eggs will hatch in about 3 days and the larvae will survive off of their yolk sacs for an extra 2 days. Once they lose the yolk sacs you can crush pellet food into a fine powder to feed them.
When the fry turn 7 days old you can try introducing them to larval brine shrimp and micro-worms. In a month you can add water fleas and adult brine shrimp to their diet.
The juveniles will mature in about 2 to 3 months. At this point they can join the adults in the main tank.
History and First Sighting
The Corydoras genus has been known for much longer than you might think.
The first species (Corydoras geoffroy) was discovered way back in 1803.
Many of the popular aquarium species were discovered through the 19th and 20th centuries.
For example the Bronze Cory Catfish was discovered in 1858 and the Julii Cory was added in 1906.
The genus was introduced to the American pet trade in 1915 and they experienced a surge in popularity from the mid-70s to the early 90s.
Captive breeding programs began in order to produce more robust and less delicate specimens. Wild specimens are still available but they are much more sensitive than those bred in captivity.
New species are still being found to this day with the most recent discoveries made in 2016. The newest species are not yet available for aquariums.
Species Summary Table
|Other Common Names:||Cory Cat, Corydoras|
|Scientific Name:||Corydoras sp|
|Distribution:||Central and South America|
|Minimum Tank Size:||10 gallons|
|Tank Mate Compatibility:||Peaceful Nano fish|
Should You Keep Cory Catfish? (Summary)
There is a whole world of Cory Catfish out there.
Their small size makes them a wonderful pick for Nano tanks and miniature setups. There are many different species to choose from with each one fitting into your aquarium in their own way.
They might even help you keep your tank free of tiny pests.
There are many different species to choose from and even the most attractive ones are friendly to beginners.
A group of these fish will liven up the bottom of any tank. While they may not be the most fun to watch they find their own way to make themselves stand out.
They are extremely undemanding and do not even need to be fed as much as other fish. All in all, the Cory is the perfect Catfish species to test the waters with.
What is your favorite type of Cory Catfish? Let us known in the comments section below…