Cory Catfish Care Guide
Corydoras, commonly referred to as cories, cory catfish and cory cats are one of the most popular freshwater fish. They’re relatively small, extremely peaceful, quite hardy and do well with live plants.
I’ve kept many different types of cories over the years, and for the most part they have pretty similar requirements. I’ll go over cories in general today, but keep in mind there are over 160 recorded species of Corydoras, and if you’re keeping a unique species, they may have different requirements.
I’ll also address what I think of as a false myth in the fish keeping world with regards to cories and substrate.
Origin
Tank specs
Unless you are keeping a dwarf species, it's a good idea to start with a 20 gallon or 75 liter aquarium. Anything with a larger footprint, versus a taller tank is a good idea since cories are bottom dwellers. That means that they will scoot around on the bottom of the tank rather than swimming up and down the water column.
When kept in small tanks they spend a lot of time glass surfing, swimming up and down frantically. That’s a sign of stress and could be an indicator that something in their environment isn’t working for them. When deciding how big an aquarium to get for your cories, keep in mind that they are social fish and should be kept in groups of at least 6. You can keep schools of different species together, but it’s a good idea to keep at least 6 of each species.
Smaller dwarf species can be kept in 5 gallon tanks, though more space is never a bad thing. With pygmy cories, it's a good idea to keep them in groups of 10 or greater.
Make sure to provide cories of any size with plenty of hiding spots. Caves are greatly appreciated!
While not essential, live plants make a terrific addition to any Corydora’s habitat. They are not exclusively detritivores, they do enjoy sifting through detritus and other organic debris.
Soft sand is the perfect touch to any cory tank. You can observe them spending much of the day foraging, by sifting sand through their gills. It’s not an absolute must have for a cory tank… I’ve seen them live healthy lives in gravel bottom tanks, but they do seem to appreciate sand and there is something fun about watching them sift through sand with their barbels or whiskers.
Personally, I always make sure to provide them with some soft sand. Pool filter sand works if you’re on a budget, but even softer would be some Caribsea super naturals, sunset gold - my favorite.
Water parameters
Temp 72° - 80° F , 22° - 27° C - this can vary a bit depending on species you’re keeping so look into this before purchasing a cory.
pH - slightly acidic to slightly basic 6.5 - 8 —- wild caught cories can tolerate more acidic conditions down to as low as 5, but captive bred ones shouldn’t be subjected to such low pH.
KH fairly wide range of 3 - 10 degrees.
GH - not something that is included in a lot of cory care guides - I usually aim for low to medium levels from 2 - 5 degrees.
Ammonia 0 PPM
Nitrite 0 PPM
Nitrate under 20/30 PPM
Corydoras are quite hardy. Even though they most often live in interconnected bodies of flowing water, they have evolved to temporarily live in bodies of water that get separated during dry seasons. It’s pretty common for these small pools to drop in pH quite drastically and to observe large temperature fluctuations between day and night as the sun can quickly warm up small pools. However, as a fish keeper your goal should always be to provide a safe and stable environment for your fishes.
Appearance
Cories grow to about 1 - 3 inches or 2.5 - 7.5 cm
They almost always take on this shape (pictures below), actually as far as I know they always look like this. Rather normal looking catfish, a little taller than your standard flat catfish. Unlike other catfish, cories are armored. With tough scale like structures called scutes and a sharp often venomous point on their dorsal fin, they are not to be messed with! They come in a variety of different colors and patterns, though they’re often light to dark gray with red, emerald, gold or green hues. Stripes and patterns are common, but vibrant colors tend not to be. They are still gorgeous fish with beautiful metallic shimmers and interestingly woven scutes structure. Their scutes are pretty large and remind me almost of overlapping medieval armor.
One of the most notable aspects of cory appearance are their barbels, or whiskers for the layman. It’s certainly one of my favorite aspects of the Corydora, and one that gives them their cute charm.
Behavior
Cories are bottom dwellers, and spend the overwhelming majority of time foraging around on the bottom of the aquarium. I’ve already talked about sand, and how they spend a lot of time sifting sand through their gills. Personally, I really enjoy observing this natural behavior of theirs!
Some other things to note about Corydora behavior is that they are pretty skittish. In aquariums that get a lot of nearby foot traffic, they can get accustomed to people being out and about. But in tanks that don’t get tons of human activity nearby, they grow accustomed to not seeing people and will dart into hiding the second anyone goes nearby. The more time you spend sitting near your tank while you feed them, the more you can teach them to associate you with food, which will help to draw them out.
Cories are an extremely peaceful fish. I have never seen them mess with eachother, other species of fishes or even juvenile shrimp, though I wouldn't put it past them to eat newborn shrimp if they ended up right in front of them.
You may notice that your cory catfish likes to swim up to the surface and then will dart back down to the bottom of the tank. That’s because they can breathe air. They take a gulp, and then unlike mammals who pass air through our lungs, cories pass air through their intestines where oxygen is extracted. Please don’t ask me where the rest of it comes out! Let’s just say the jacuzzi is bubbling.
They’re able to breathe air because in the wild, the slow moving bodies of water that they live in can temporarily get cut off from main rivers, becoming stagnant pools of water with little to no dissolved oxygen content. It’s interesting though to notice, that there doesn’t appear to be a rhyme or reason for when they gulp air in the home aquarium. Even with saturated oxygen levels, they appear to enjoy catching some fresh air.
Diet
A lot of people tend to think of bottom feeders in the aquarium as being herbivores, but that certainly isn’t the case, especially when it comes to catfish. Cories are omnivorous fish, that should enjoy a varied diet of food.
I often feed them extra of whatever my other fish are getting. Flakes, pellets and wafers are happily accepted as well as frozen foods like blood worms and mysis shrimp. They really go crazy for live foods as well. I feed mine young scuds.
In terms of fresh veggies, I throw in zucchini and blanched broccoli. They seem to get quite excited initially, but quickly lose interest after a few bites, unlike higher protein foods which they will pick away at till they are completely gone.
Tank mates
Cories make a great addition to pretty much any community tank. They do well with a variety of smaller fish like tetras, danios, rasboras and barbs as well as larger community fish like angels, severums and acaras. They are also fine to keep with breeding shrimp colonies. Despite their venomous dorsal spine, they do not do well with larger aggressive fish like oscars or arowanas.
Breeding
Many species of cory cats will readily breed in aquariums. I’ve unintentionally bred panda cories in the past in a Fluval flex 15 gallon with other small community fish and shrimp present.
Females are a little more robust than the slender males. That’s due to the fact that they need a little more space to carry eggs.
Sometimes dropping the temperature of incoming water a couple degrees during a water change is enough to simulate monsoonal spring storms and trigger breeding. Cories scatter their eggs, so providing a lot of hiding spots for eggs and fry is important if you wish to successfully breed them in your display tank.
In some species, breeding may require more specific triggers with regards to pH, KH, live foods or a combination of any of those elements in addition to temperature.
Myths regarding substrate and other facts
One of the most common myths regarding corydoras is that they can’t tolerate any sharp rocks or non-sand substrate in aquariums. I have serious reservations about this thought. I’ve seen plenty of cories live long healthy lives in gravel or planted soil bottom tanks, even tanks with no substrate.
I do think that there is some truth with regards to keeping only sharp edged substrate like course sand or seachem flourite. Naturally, cories use their barbels to search around for food along the bottom of the tank. If the entire bottom of the tank is lined with sharp substrate, it could lead to deterioration of barbels.
It’s a good idea to cap areas with sharp substrate or provide other more adequate spots for your cory cats, if the whole bottom of the tank is full of sharp areas. Some sharp rocks here and there won’t lead to the destruction of your cories' barbels. In the wild, cories live with a variety of different types of objects and come across sharp sticks or rocks fairly often. If one area isn’t suitable for them, they can swim to another that is.
If your corydoras are losing their barbels, it’s worth considering substrate… Like if you only have sharp stuff across the whole bottom of your aquarium. From what I’ve seen over the years, it’s far more likely that poor water quality or diet are to blame. So make sure that your water parameters are in line with what I talked about earlier, and that your cories are getting a healthy and varied diet.
The last myth I want to address today is with regards to spelling. One cory, two cories. Cory’s would be like talking about a guy named Cory. For example, if that guy Cory had a bunch of cory cats with barbels, it would be Cory’s cories’ barbels.
I hope you learned a lot today! Or even a little bit. If you have any questions, drop it in the comments 💬