Corydorus Catfish: A Primer
Corydoras catfish are one of the bread and butter fishes of the aquarium hobby, and have been since the 1930's. Bewhiskered charmers, Corydoras cats are, in many minds, THE catfish to buy for your tank.
It's the winking charm and droll attitude that makes Corys so popular. In this post, I'll demystify keeping these fish, as properly kept, Corys offer years of enjoyment. Keeping Corys in groups is the thing to do, for their security and your enjoyment. A dozen of the smaller species in a 55 gallon is not too many. Double or triple that for the tiny dwarf species.
First, nomenclature. The Genus name - Corydoras, was erected in 1803 by the French naturalist Bernard Germain de Lacιpθde with the first discovered and described species; Corydoras geoffroy. At the time he thought the head of the fish was covered by bony plates (it isn't), so he called it Cory for a cuirass (a helmet) and doras for skin, which in this case was on the head. He anglicized the Greek 'Kory' for the Genus name. So Corys are literally 'helmet headed'.
Since that time over 350 species of Corydoras have been discovered, with more discovered almost monthly. Around 150 have been named to science; the others must wait their turn. Until then, they receive a 'C' number, such as C-153, meaning the 153rd discovered that does not have a scientific name.
Corys are native to leaf-strewn streams of the Amazon basin, where they hunt aquatic worms, insect larvae and small crustaceans among the leaves. In the vast majority of the time their stream mates are Apistogramma species Cichlids and swarms of small, colorful tetras. Lurking predators like the Genus Crenicichla and in some waters, Hoplias, mean that both the Cichlids and the Corydoras key on the tetras. If the tetras are acting cool and unconcerned, so then are the Apistos and Corys. If the tetras scatter en masse, the Apistos and Corys take cover. That dynamic is a clue on what to keep with your Corys to see natural behavior.
For Corys to be at their best, keep them in groups, with the more you have the better and more entertaining they'll be. They are perfect for the planted aquarium as long as they have swimming room at the front, and they are perfectly peaceful fish.; even the smallest tetra species is safe with them. Corys all prefer soft neutral to acidic water, down to pH 6.5 or lower, but are adaptable; but don't go over 7.5 and moderate hardness if you wish to keep your Corys for years instead of weeks or months. Almost all the common Cory species are farmed, thus can adapt to different water parameters, but wild caught examples MUST have soft, acidic water to live, much less thrive.
As for feeding, Corydoras never met a worm they didn't like. Frozen or live, if they are suitable size, they'll very happily eat them, and do best if they have them. Small frozen shrimp, like Mysis, are good, as well as high-quality small sinking pellets. Mine adore frozen black mosquito larvae, and live California black worms.
Another clue is the leaves; Corys must have a softer substrate. Poor water circulation and sharp stone gravel can abrade whiskers, and since Corys use them to detect food, makes them crippled for life. Rounded pea gravel is OK, but make sure your tank is well filtered. It's strongly indicated that higher levels of Nitrate sink and hug the substrate, which most cory species spend the vast majority of their time, and can also lead to whisker degradation.
Thus sandy substrates are best, or even better, covered with suitable leaves. I use the original formulae of Eco-Complete with my Corys, as it's quite sandy. All of them look best over darker substrates, especially the lighter-colored species. All will be more richly colored on a dark substrate.
So, in a well-planted, well-filtered, soft water aquarium with tetras and dwarf Cichlids, Corys feel right at home. Many, many species are available, but you can keep them all just the same.
Now, some species.
Perhaps my favorite of the family is Corydoras guapore, of the Guapore River drainage in Brazil. I see them the most, as I have a dozen of them in the 75 to my right as I write this.
Topping out a shade over two inches, C. guapore is a very yellowish, brown-speckled bronze with a black blotch on the base of the tail, reaching up to the back of the adipose fin. The yellow bronze are on the top and bottom rays of the tail, which is otherwise clear, and on the lead rays of the other fins. Eyes are a silvery yellow. The snout is petite and points rather out, instead of down like most corys.
C. guapore spend a lot of their time up in the plants cruising the leaves for tidbits, and often rest on the leaves, even rolling over on them in their sleep. Sinking food brings them down. Agile little fellows, mine pursue live Daphnia with gusto, just as fast if not faster than the tetras do.
Since they are small, live, frozen and prepared must be suitably sized. A vegetable-based pellet is strongly recommended, as it intensifies their colors.
As they are quite small, very passive fish are the rule. Mine are tanked with Lemon and Rosy tetras, marbled Hatchet fish and a dwarf Ancistrus species. They have proven to be quite durable at 77 degrees, but from my research, that's the upper limit for this species.
In breeding, the school does it en masse and the vast majority of the eggs are on fine and broad-leaved plants. The fry grow rapidly on a diet of live microworms, followed by baby brine shrimp and sifted Daphnia. Mixing the microworms with small, pelleted foods toward the end of the time with the worms usually gets the little Corys to accept prepared foods.
A cooling, perhaps five degrees below tank temperature, twenty percent water change, when there's a thunderstorm in your area about half the time triggers breeding. Filtered rainwater is best for the partial change, but distilled or reverse osmosis water can work.
The school does very little roaming at night, and most of the time sleeps in the nooks and crannies of a large piece of driftwood in the tank.
A very cute, rather colorful little fish. May take you some time to find them, and they aren't cheap since they are still mostly wild caught and in demand, but well worth seeking out if you have a suitable tank for them.
The first Cory widespread in the hobby and first commercially bred is Corydoras aeneus, the Bronze Catfish of Trinidad; an island off the coast of Venezuela.
This fish was introduced freely into the US hobby in 1933, making it the grand potentiate Cory of the aquarium. Simply a green-yellow bronze on top and on the head, with a pinky-white lower half in it's native self, the Bronze Catfish has been around long enough several man-made variations have appeared. Most common is the albino form, where the fish is a pinkish white, and a long- finned form, which hinders the fish's ability to swim.
Wild caught examples are glittering little fish, though the more naturally-colored farmed form does shine a bit in the light when properly kept.
C. aeneus tops out at 3 inches, making it one of the larger species. They are very omnivorous, and will even eat soft algae if they find it while prowling the bottom realm. Thus, adding blanched fresh vegetables and fresh fruit will result in the best color and health for your fish. Frozen shrimp, insect larvae, worms, and live worms if available and clean, are very avidly eaten. Mine liked peach halves a lot.
Males are a touch smaller and slimmer than the females, which are wider when viewed from the top and visibly heavier-bodied than the males. Best temps for C. aeneus are 75 to 79 degrees. They do best in moderately soft water with a pH between 6.5 to 7.5.
Planted tanks with driftwood and stones are perfect for a group of Bronze Catfish. They hide somewhat under the bright light necessary for planted tanks, so floating plants over the swimming area are very helpful for proper viewing of this species.
In such tanks, Corydoras aeneus are almost ridiculously easy to breed. A cooling (perhaps five degrees below tank temperature) with filtered rainwater, distilled water or reverse osmosis water when a low pressure system is in your area will nearly always result in eggs all over your tank in the morning.
It's very worthwhile to home breed your fish, as the offspring will be healthier and much more colorful than the parents. In my culture manual section of foods for egg-laying fry, microworms are the perfect first food for your baby Corys. It's here
There are several variations in colors of wild C. aeneus, so keep your eyes out for them.
On to Part 2
When a finger points to the moon, the imbecile looks at the finger.
Omnia mutantur nihil interit.
The more you read, the more things you will know. The more that you learn, the more places you'll go