With 150 formally described species, and perhaps more than a hundred undescribed species, the genus Corydoras offers great possibilities for fish keepers. All species are easy to care for, relatively undemanding fish with great personality. Many of them are readily bred. For the average fish keeper they are relegated to the "cleanup crew" and kept singly or in very small groups. Even under those conditions, they can be interesting fish. Kept in larger groups, they really shine and can become the focal point of a lively aquarium.
Corydoras are social fish - they should not be kept in groups of less than three. They appear to be happiest in groups of six or more. With the right selection of fish and appropriate aquascaping you can enjoy almost constant activity as they swim around a community tank.
Corydoras catfish have been kept by aquarists for over 100 years. The most popular and readily available species are Corydoras aeneus, the Bronze cory, and Corydoras paleatus, the Peppered cory. Both species are extensively bred in captivity. Long-fin and albino versions of both of these species exist. They are both are available in most pet stores, including national chains like Petsmart and Petco (in the US). Peppered corys, which are native to southern Brazil and northern Argentina, prefer cooler water; this is especially true for wild-caught fish.
Other popular species include the Panda cory (Corydoras panda), Corydoras trilineatus (often mislabeled as Julii corys) and Corydoras sterbai.
There are six species commonly known as dwarf corys. These fish get up to about an inch and a half in size. Three species are more commonly encountered - Corydoras habrosus, Corydoras hastatus and Corydoras pygmaeus. The others are harder to find - Corydoras cochui, Corydoras gracilis, Corydoras xinguensis.
Dwarf corys are some of the more entertaining species. Given their small size, it's possible to keep them in fairly large groups, so you can observe their shoaling behaviour. All except Corydoras gracilis are considered relatively easy to breed.
Corys live feed primarily on the bottom of the tank. They find food by sensing it with their barbels. Many people get catfish specifically for that reason - to clean up uneaten food. If you rely on that, your corys might not get enough to eat. It's a good idea to feed them sinking food that they will have a chance to get at before all the other fish do.
Many people suggest feeding them just before you turn off the lights at night. Once the tank is dark the corys have an advantage when it comes to getting food, because they find food using touch, not sight.
Corys do well on a mixture of live, frozen and dried foods. A high quality diet, right in live of frozen food, is important to get them into breeding condition.
Most corys prefer softer water with a pH around neutral, but this varies from species to species. If you have a specific species in mind, look it up in Planet Catfish's Cat-eLog. Corys tend to be fairly tolerant of water conditions, but you are unlikely to get them to breed unless you meet their specific water quality parameters.
Many Corydoras species are considered easy to breed. While the specific conditions vary, most will respond to a series of water changes a few degrees below the temperature of the water in the tank. Before trying to breed corys, it's important to get them into breeding condition. This usually requires a high quality diet rich in live or frozen foods.
Many people have reported that a water change coupled with a drop in barometric pressure will trigger corys to spawn. Other people have found that difficult fish will spawn when water is added from a tank with other breeding corys.
The best resource for beginners is Plant Catfish. Their Cat-eLog has an extensive collection of images. Their forum has a section called "What's my catfish?", which provides identification for unknown species. And Shane's World is a great collection of articles.
For the dedicated Corydoras keeper, there's Corydoras World. Run by Ian Fuller, one of the top Corydoras keepers and breeders, the site has a wealth of information. Most of the information on the site is subscription-only. At £15.00 (about $30 US) subscriptions aren't terribly expensive, but enough to deter the merely curious.
Tom on March 17, 2013:
If you have Corys with other types of fish... a very good food to mix in with your other fish foods --- especially if your other fish are Black Tetra size or larger --- that your other fish will mostly ignore (but that the Corys will eat)... is decapsulated brine shrimp eggs. You can get them from brineshrimpdirect.com Add a couple of tablespoons to 7 oz. of regular or freeze-dried fish food. The brine shrimp are so tiny that most fish (except guppies and such) ignore them; but the corydoras catfish love them! They eventually sink and are greedily consumed! A little goes a long way!
Jpac90 on July 21, 2012:
I have my temperature set at 28c for my discus would corys survive this temperature?
DrHoo on April 25, 2012:
If only humans were as agreeable as Corys, They get on fine with themselves and other species, keep the place clean, have genuine sense of humour, don't overpopulate and are beautiful to watch. Your hub is really helpful I Ramjohn, keep on fishkeepin on.
I Ramjohn (author) on March 05, 2012:
My guess would be to give them sinking pellets - they should make it to the bottom before the other fish get them. I wouldn't worry about the shrimp - corys should be tough enough to compete with them for food, especially if they are hungry.
Jimbo on March 03, 2012:
I have a heavily stocked 75 gallon tank and everything is really good.I do 30% water changes once a week and don't overfeed.But,I don't thing my corys are getting enough to eat When I try to feed them the other fish get it before they do. I have fed them after lights out but I thing the amano shrimp might be getting it before them.I see how those amano shrimp are when the lights are on,and they try to steal the food from the fish as best they can,and their pretty good at it. I know my corys aren't getting enough. What should I do?
Opalrose on February 20, 2012:
Listen, ray71384, U need 2get a life and stop being so negetive.
NO ONE NEEDS TO HEAR YOUR POTTY MOUTH AND PUT-DOWNS.
This is not the type of site for yur negetivity, SO SHUT YUR MOUTH !
If u don't like or care for this VERY HELPFUL INFO, then stay off the air.
U NEED 2GET A LIFE, VATO !!
ray71384 on February 13, 2012:
does it really matter how many species there are...who gives a fluck...y'all are all losers smh
swamp fox on August 21, 2011:
Do they eat other fish in the tank. We left town and came back. three tetras were gone? No sign of them. Two corys in the tank and one tetra left.
vidar on December 22, 2010:
Thanks for the advice. bosh for the heat is over rated.
vidar on December 22, 2010:
Thanks for the advice bosh for the heat is over rated.
Pixigutz on November 11, 2010:
Corys (particularly the peppered variety) are usually a great mix with bettas. Ensure you have hiding spaces from the light for your Cory, and I would recommend some aeration; predominately use their labyrinth to breath oxygen from the surface, while corys only to this if the oxygen levels in the water are low. If you live in a temperate or tropical climate there should be no need for heating, although this may be required in winter, as neither bettas or corys like temps much under 20 deg Celsius or so. Live plants are also good idea.
LenaP on October 20, 2010:
I have seen the corys recommended with betta, partly because they don't require aeration.
warjna on September 27, 2010:
Hi! I just bought two corys to go in my two tanks with my bettas (2 females, separate tanks). One is an albino and the other is dark silvery. I had a brain fart at the store, should have asked if the tanks now need to be aerated? I'm not seeing anything about it on any of the websites I've searched. Also, I brought them home in the same bag, and one kept chasing and nipping at the other. Am I going to have problems with them together with the Bettas?
I Ramjohn (author) on August 29, 2010:
Corydoras aeneus, the Bronze Cory, gets up to about 3 inches/7.5 cm long - females larger than males. Pygmy cories, on the other hand, reach a size of only a little over an inch, about 3 cm. Brochis, on the other hand, sometimes sold as the Emerald (or Green) Cory, gets much bigger - 3 inches or bigger.
JRaab on August 29, 2010:
how big do they get
JC on March 09, 2010:
i have a pond....3500 liter one.....and i have several different corydoras, i have found egg under the leafs of a couple plants.....i have grabbed them and put them on a separated 50 ltr tank...with that blue thing to avoid algae and well airated....is there anytnhing else i need to do ?? how long do i have to wait to know if the eggs stilll good or not ?? any other advise pls ??
dar on February 25, 2010:
Just found this site, interesting and informative reading as I loveeee Corys (my favorite)! Congrats to 2 yrs.
Cory on December 15, 2009:
Well how seriously can you take someone with a stoner towel as his avatar anyway?
Woo on August 29, 2009:
Obviously vanhove is sadly mistaken, either that or he is unable to count. If only as a visitor it is possible to visit corydorasworld.com where there are nearly 300 species listed. Most of them with names but there is the C list and the CW list for the ones with no names given as yet.
token on September 02, 2008:
they r easy to breed
Adrian Walker from Magnolia, AR on May 23, 2008:
Well written, both the article and the reply to that rather sad comment. Keep up the good work
I Ramjohn (author) on February 18, 2008:
In his "Checklist of Catfish" published in the journal Zootaxa, Ferraris lists 153 valid species. At least one species has been described since then. So no, I think "over 150" is a pretty good estimate.
Ferraris, Carl J., Jr. (2007). "Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types" Zootaxa 1418: 1–628
vanhove on February 17, 2008:
You are completely wrong about corydoras, there are only 99 species of those catfish so don't write hubs about stuff you don't know about. You probaly don't even own chia pets. Those lions are extinct.