Of the numerous types of fish kept in aquariums by hobbyists, the least appreciated fish, but one of the most commonly kept is the Corydoras sp.
Most commonly, they are purchased as bottom cleaners and very seldom for their interesting habits or their looks. To me, this is disheartening. When kept healthy and in a suitable environment, they can easily be as fascinating or striking as many of the more colorful fish in an aquarium.
What is Corydoras Fish?
Corydoras are generally bought from pet stores in very small numbers, or singularly as cleaners for community tanks. Although this does not seem to prevent the fish from performing the task for which it was bought (cleaning), they are actually schooling fish and are much happier in a group of 4 or more.
Watching a school of any of the scores of varieties of these catfish work its way around a tank is a fascinating sight.
Corydoras and their relatives (Aspidoras and Brochis) are generally colored so as to be difficult to see sitting on the bottom of the streams in their natural habitat. They are usually gray to silver, with darker spots or splotches of gray/black, or they are flesh-colored, with dark spots or stripes, or some combination of both. There are a few that have a darker brownish color. The colors may not be flashy, but some of the patterns are very interesting.
Of the dozen to a dozen and a half species I have kept, I can’t say that any did not keep my attention. Their shape, their movements, and their color provide for a very interesting and entertaining fish.
Another thing to note is that these fish are able to move their eyes to some degree. The movement gives the impression of a wink.
These fish will feed on most of the standard aquarium fare and relish tubifex and oligochetes, sand, or substrate worms.
Breeding Corydoras Catfish
Breeding these catfish may not be all that difficult. Of those that I have kept, I have attempted to spawn five species, and have been successful with four to date. My success has been accomplished in two very similar ways.
First, when attempting to breed these fish, buy 6-12 smaller sized fish of the species you want to try. Get hold of some form of literature that will tell you how large the particular species gets, and buy them at half of the full size, if possible. This will help to ensure that your stock is not much older than one year of age.
Buy them during our summer months, if possible. The reason for this is that except for only 2 or 3 species, almost all of the catfish bought in stores will be wild-caught specimens. The majority of these catfish breed in the Amazon in the spring, which would coincide with cooler spring rains. So, if you buy them during our summer, they should be a nearly one-year-old plus.
The attempts to breed them the first autumn after buying them probably will not be successful. Most of the literature I have found says that the majority of catfish do not mature until after one year (probably 1 1/2 – 2 years).
Keep your fish healthy and well-fed for a year. By buying 8-10 you can help to ensure a good sex ratio, as well as having enough for breeding in the event of casualties.
I keep my fish in my basement, so temperature changes are not too quick to get to extremes of heat or cold – even here in Minnesota. This allows for being able to more easily regulate my tank temperatures for the procedure I’m about to explain.
My tank temperatures seldom exceed 80°F, even in the hottest weeks of the summer. As fall approaches, I place heaters into my tanks to hold them at 72-74°F. As preparation for breeding, I set up a tank in one of two ways, (1) a larger tank (20-30 gallon long), complete with gravel and wide leaf rooted plants; or (2) a bare 10-15 gallon tank with just a sponge filter.
In either case, I let the tank stand for 2-3 weeks and monitor the temperature.
(1) When the water temperature drops down to 68°F. I move my group of breeders to this tank. The temperature will usually get the spawning started in 3-5 days. The eggs will be laid on plants and on the sides of the tank.
Once I notice the spawning has occurred, I will wait 24 hours and then move the plants to a bare tank and gently remove the eggs from the sides of the tank and move them as well for hatching.
(2) As my smaller tanks are closer to the ceiling, this procedure differs only in that just placing the fish in the tank won’t do it. The temperature of the tanks near the ceiling of my fish room seldom falls below 72°F, even without a heater.
Thus, I will usually do 20% water changes for 3-5 days, with cool aged water, to encourage spawning. As the tank is bare, all eggs will be laid on the sides of the glass. I then remove the adults 24 hours post-spawning.
The important point here in the spawning procedure is the decrease in temperature, dropping the temperature from 72-74°F to 66-68°F. Don’t worry about temperature shock to these fish, it doesn’t bother them. Also, Cory cats are not as prone to diseases like velvet or ich, as other fish seem to be.
Some diseases that cats do get are mouth funguses, from rooting around in either a very dirty substrate, or because of injury from gravel that is too sharp. Also, common are tuberculosis and various intestinal bacterial illnesses. Body flukes or parasites are not uncommon either. This is usually evident if you see them scratching themselves on things the tank.
Feeding catfish is pretty easy. They will consume most anything that is fairly soft and not too large. I prefer Tetra pellets, flake food, Doromin (crushed), and frozen brine shrimp.
Common Corydoras Catfish Species
Some of the more common species are: Corydoras paleatus, C. aeneus, C. trilineatus, C. jullii, C. metae, and of the Brochis genus: B. splendens is the most commonly seen. Recently, a species of Aspidoas has been fairly available, namely A. lokoi.
These types of cats are relatively easy to keep, generally stay healthy, live long lives in the aquarium, and provide good general interest for those that keep them. It would be well worth the time and effort to specialize in these catfish, or just to keep them in a community tank setting.