The Colors of Corydoras

by Don Kinyon

There are a few "new" imports of Corydoras catfish coming in from South America lately that some Cory cat nuts, such as myself, are excited about. Some of the most colorful, and promising to be the most popular fish, are a group that may or may not be aeneus. They resemble this most common of catfish in body shape and temperament, but tend to have a very bright iridescent stripe arcing from just behind the eye all the way to the tail. The color of the stripe can be green, orange, or red.

It isn’t my purpose to argue the point of whether or not these fish are indeed a color form of aeneus; I’ll leave that to the scientists. I will attempt to give, from a hobbyist’s point of view, the similarities and differences of the fish both to each other, and to the common aeneus.

I have kept each of these varieties in my tanks for at least a year and some for much longer. They are similar in appearance, but the behavior and especially egg production, in my experience, are much different. This doesn’t conclude that the fish aren’t all aeneus, I’m sure, and I have no way of knowing that the fish were the same age when spawned, as some were young and some adults when they came to me. All the fish were approximately the same size when they spawned, and all had been kept under the same water conditions and fed the same foods.

The chart will better show what I mean:

Fish Total females Total spawns Total eggs Average eggs per female per spawn
Albino Aeneus 3 3 218 22.4
Laser Green 2 8 351 21.9
Red Stripe 5 2 58 5.8
Orange Stripe 1 2 199 99.5


As you can see, the numbers vary greatly.

This is a very unscientific observation; I have no way of knowing that all the females present took part in the spawn, and the number of spawns are probably not sufficient to get a good idea of the true tendencies of the fish. Some Corys have a tendency to eat the eggs before they can be moved, and others don’t, and so on. The chart only shows the limited experience that I’ve had with the fish in my own fish room.

The coloration of the different varieties of adult fish is varied. The brightest of the bunch by far are the "laser green". The stripe glows so brightly that many people avoid buying the fish for fear that they have been shot with dye or hormones. I was skeptical myself, but found the fry retain the color, so I don’t believe that the fish were "worked on" at all. In natural light, the color can take your breath away. The "red stripe" have a lot of color, though not as much as the greens. They have a much darker body color, and the iridescent stripe is red-orange. The "Peru orange stripe" has the least iridescence, and the body color is lighter. The stripe is pale orange, and some fish don‘t show any iridescence much behind the shoulder.

Another difference I’ve found with the fish is the hardiness of the adults and fry. Of the common albino form, which I’m fairly sure were tank- or farm-raised, there were no casualties in the years that I kept them. The wild caught "Peru orange stripe" were much the same, as I still have the same three after two years. The wild caught "red stripe" were in great shape when I received them, but there were still a few deaths within the first two months; after this initial period, they all survived. The "laser green", on the other hand, can make one crazy trying to get them to live in captivity. These are also wild-caught fish. I started out with seven specimens and it nearly made me cry to pay out that much money for fish all at one time, especially after they started to die off. By the end of the third month in my tank, there were four left: luckily enough the survivors were two males and two females.

The placement of the eggs when spawning varies between the color forms, also. The "laser greens" put eggs mostly on the front glass (usually the only clean pane in my tanks), while the reds hide them mostly among the plants, and the orange form haphazardly laid eggs anywhere that they will stick. When spawned in new surroundings, as were the green and orange varieties on occasion, the fish held true to their own patterns.

The fry of all the color strains seem to be hardy enough, though I still occasionally lose broods of the "laser green" for no apparent reason. The fry of the "Peru orange stripe" are as healthy as any of the common aeneus that I’ve had, while the "red stripe" grow very slowly and never seem to eat as ravenously as any of the others. I’ve had spawns of the three color varieties all at around the same time, so I was able to observe the differences between the fry firsthand, comparing directly. All the fry were raised in the same conditions and fed the same foods; micro worms to start, and after a few days, baby brine shrimp and fine flake food. The water was from the tap: 7.4 pH and 140 ppm of total hardness.

Water changes were done twice weekly at 25 percent. The substrate was fine sand (play sand from Lowe’s-two dollars for fifty pounds), sponge filters were in all the fry tanks, and there was approximately the same amount of fish-per-gallon in each of the tanks.

At one month, the difference could be seen in the three color varieties. The "red stripe" had a very dark body color, while the orange and green colors had lighter coloration. The "laser green" already showed the start of the iridescent green stripe above the shoulder.

At two months, the differences were even more pronounced. The dark body coloration of the "red stripes" got even darker, and they started to show the iridescent line. The "laser greens" got even brighter, while the "orange stripes" failed to show much color as yet.

At three months of age, the "laser greens" are a smaller version of the adult. They are at a length of over 1" and show all the color of the adult. The "Peru orange stripe" are about the same size, but show only part of the adult coloration. The "red stripe" are almost as colorful as the adults, but only 3/4" long.

Whether these fish each get their own identification or are decided to be a color form of the Corydoras aeneus, they are a pleasant resident in any community tank, or a delight in a species tank or breeding setup.

For More Information:
Planet Catfish. Jools has done a great job on this site-great picture gallery and good articles in Shane’s (Linder) World.

Aqualog. All Corydoras by Glaser, Schafer, and Glaser. ID type photos and basic information on many Corydoras
Corydoras by Werner Seuss. Much breeding and general information, pictures on most Corydoras cats
Back to Nature Guide to Catfishes by Dr. David Sands. Good information and pictures on many catfishes, including Corydoras
An Atlas of Freshwater and Marine Catfishes by Dr. Warren Burgess. Large work on most any catfish found. Some of the newer imports are excluded, but information on all included fish is accurate and plentiful.

Thanks to Ernest J. Gemeinhart, Cory nut extraordinaire, for putting up with my questions.

This article first appeared in PVAS’s Delta Tale, Vol 32, # 1