By Don Kinyon
Corydoras atropersonatus has been around the hobby for a long time, but never seemed to be common in pet stores or even in aquarium society events. It’s not one of the more colorful varieties but an attractive fish in its own right. It was described by Weitzman and Nijssen in 1970 but from some accounts was available in the hobby long before that time. In the wild, atropersonatus is found in northern Peru and in Ecuador in the Rio Nanay and surrounding systems in fairly soft, acidic, slow moving waters.
This is a fairly small Corydoras, with the females reaching a little over two inches and the males staying somewhat smaller. The base coloration is a very light brown to almost white, with black spots throughout. The pattern varies from regions and even from one individual to another. The fins are clear, with the exception of some individuals’ dorsal fins, where some faint spots can be seen. This Cory has a black mask that extends from the top of the forehead in front of the dorsal, through the eye to the bottom of the gill plate. Very simple pattern, but still very pleasant to the eye.
I was fortunate enough to receive a group of these Corys from another hobbyist and was looking forward to a new (to me) species. I brought them home and put them in a 40 gallon cube-style tank where they would be sure to have some room. There were eleven fish in all, and by their appearance looked like a good breeding group: four females and seven males. Their new home had a thin covering of fine sand on the floor, a couple pieces of bogwood and one Anubias plant for décor. There were two large bubble-up sponge filters to keep the water clean and two yarn mops for cover: one bottom mop and one suspended by a float. There was no heater in the tank, so it fluctuated between 67° and 75°F.
Water was straight from the tap, which is 160ppm TDS and 7.2 to 7.4 pH. The fish all seemed to be comfortable in their new home and were very active right from the start. One thing about this species is that they do almost everything as a group. I have witnessed large schools of Corydoras in the wild swimming as a group, but once in captivity, most lose the urge to stay together, to some extent at least. These Corys were almost always in the tight group, and fun to watch.
From the beginning they were fed both dry prepared foods in the morning and either live or frozen food in the evening. Dry foods were a variety of flake and pellet commercial foods and the evening meal could be frozen blood worms, live white or black worms or chopped earthworms. They took all foods with enthusiasm.
When the females started to show signs of “plumping up”, weekly water changes were changed to twice weekly, and instead of tap water, cool rainwater was used. All the changes were around 30 percent.
It was three weeks after the new water change schedule started that I noticed some small, dark brown eggs on the floating mop. Great! Time to harvest and hatch! After removing both the bottom mop and floating mop, I was pleased at how many eggs the fish had produced: fast count of 160. These were placed in a 5.5 gallon hatching tank with a matten-style filter and fine sand covering the bottom, along with some Java moss for cover. The water for the hatch tank was taken from the breeding tank. An alder cone was added to try and keep any fungus from spreading. In a few days’ time it was clear that the eggs were not going to hatch. Not a single fry from all those eggs.
Undeterred, I kept feeding the breeders heavily with live foods and kept up the twice weekly water changes. Another four weeks went by before the catfish spawned the second time. This time there weren’t quite and many eggs, but still around 100. These were put in the now clean 5.5 gallon hatch tank with fresh water from the breeding tank. This spawn had the same result: no fry.
Again, still confident that there would be fry one day, I persisted, and the third spawn failed as well: no fry hatched.
The fourth spawn I was not as confident, but treated the eggs in much the same way, being more careful as to cleanliness and keeping closer watch to see what may be keeping them from hatching. On the fifth day after this spawn, I spotted a tiny fry in the hatching tank. Finally! Keeping close watch after that revealed that there were five young catfish from this spawn: not great, but not zero.
During water changes the next weekend, I spotted movement under the bottom mop in the breeding tank. Upon moving the mop out of the way, several young Corydoras could be seen, and there were at least two different ages of fry, probably three! For some reason, the eggs that I missed when collecting were hatching in the breeding tank and most of the eggs that were removed were not.
It only made sense to use the method that was evidently working even though I was totally ignorant of it, so I ran to Walmart and bought two large skeins of “camo” yarn and made a whole bunch of bottom mops. With most of the breeding tank floor covered with mops, the fry had as much cover as could be provided and, in theory, would avoid predation.
Well, it worked. I’m not sure how many eggs and/or fry are eaten by the adults before they grow too large, but at this writing, raising any one of the mops from the tank floor will reveal a range of sizes of young catfish, from newly-swimming babies to half-sized versions of the parents.
I would recommend Corydoras atropersonatus to anyone, whether they are interested in spawning fish or simply observation. They are easy to keep healthy and get into condition, and they are a delight to watch!
One note I should add about this spawning and hatching method: Cleanliness is key. Uneaten food and detritus tends to collect under the mops when they cover so much of the tank bottom, so when water changes are done the mops should be moved around to clean under them, using caution as to not remove the fry with the trash!