This Corydoras crossed my path somewhat unexpectedly. I was visiting a shop when I saw a group of very young Corydoras swimming around together, they were about half an inch and sort of looked like Corydoras pygmaeus, both in terms of colour and size; but the shape was not them for sure. I asked the shop’s owner about the name of the species he had there, he told me it was Corydoras eques, I told him that I could bet my right hand that they were not and after asking for the price (which was really fair) I went home with 4 of them.
The new fish were placed in a 25 gallons tank with some Otocinclus and Corydoras panda. They did settle in pretty well and they gently started to grow to adult size. I was finally able to identify them as Corydoras napoensis, still I hesitated with Corydoras elegans for a long time because these two species are very similar in appearance. Today I can clearly say that it is Corydoras napoensis, thanks to Ian Fuller’s sketches of young fry in his already famous book “Breeding Corydoradine Catfishes”.
Corydoras napoensis comes from the Rio Napo and Rio Aguarico systems in Ecuador, from the Rio Nanay in Peru and from the Rio Atacuari and Rio Amazonas in Colombia. It is a rather small medium size Corydoras that grows to 2 inches for the females and a bit smaller for the males. There are 3 others species that are really looking like our Corydoras and very tiny differences exist to allow us to identify correctly our fish. These species are Corydoras elegans, which is very commonly found in pet shop and hard finders Corydoras nanus and Corydoras pestai.
About a year ago as my fish had reach adulthood, I had the luck to spawn these little guys. Purely by chance, out of the four fish, two were males and two were females. I set up a 6 gallon tank with fine sand, a few Anubias and a small outside filter which a 100gallons per hour filtration’s capacity. The only light for the tank is the one coming from through the window. No heater is present so the temperature is in the low 70’s high 60’s F°. A piece of driftwood and a bamboo cave are also providing to allow the fish to hide if they need to. The water was the usual tap water, which parameters are ph: 7.4 dGh: 12° dKh: 8° conductivity: around 300 microsiemens.
Thus, the four fishes were placed and that tank and they started to receive some bloodworms as daily food. Every two days a 50% water change was made using slightly cooler tap water. After two weeks of that treatment there was still no spawning but the females were obviously getting fatter! I did try to modify the temperature with the water change make it drop more or less, but still no response. I also tried modifying the percentage of water changed and made them more or less often. All to no positive response. I finally came with the idea that the water might be too hard, so I did a 50% water change with R/O water. The day after as I checked under the leaves of Anubias, I found numbers of very small eggs in groups of 10-20. I was sadly not able to observe the spawning activity and I have no idea how it went but to what I was able to read it goes as for the other Corydoras species in the typical T position routine.
Obviously only one female, the smallest, had taken part in the spawn as the other one looked like she was still full of eggs. The adults have not tried to eat any eggs. I did cut the leaves and put them in a little plastic box filled with water from the tank. I did not add any anti-fungus but only an air stone. I placed the plastic box in a dark place to help prevent fungus. After four days, the eggs hatched and, encouragingly, just a few had turned white. The young were acutely small, a few millimetres long. At this point there were siphoned and put in a 3 gallon tank. Into this I put some fine sand, a “Tetra Bilifilter “ and the water level was not too high so as not too kill the fry. After two days the fry completely absorbed their yolk sac. Liquid fry n°1 was given as first food. They were fed this during about four days. At this stage micro worms were given as their second food. I found the fry rather as slow growing, despite a good quality feeding and everyday water change. After two week I gave them some tablets for bottom feeders, but not one completely, just a quarter of it. Any left over were siphoned so as not to pollute the tank. When refilling the tank it is important to make sure you are replacing water at the same temperature and with the same chemistry otherwise you can kill some if not all of the fry.
Sadly this story does not have a happy ending. 24 hours after a water change, the fry started to die off en mass. By the time I was home more than half of the fry was dead and the surviving ones were not looking good! I redid a water change as I thought it was a pollution of the water but at this time I did not think that it could have been my tap water. Well, of course, this just finished off the remaining fry. I did not have any tap water prepared in advance for them. When this happens usually there is not any problem, but I was in a time of the year in this part of Switzerland when the water is not really good. Either it has some organic pollution or a big dose of chlorine. Whatever it is I learned the lesson and will not commit the same crime again!
So far I have not attempted to breed them again, but I am considering doing it again pretty soon. Instead of putting the young in a tank of their own I think I will put them in a nursery, which would be in a big tank. This way I would avoid fouling the water too fast and will also make water changes less necessary, well sort of! I have found other newly hatched Corydoras to be very hardy and can be almost passé about different water characteristics without any problem. I did this with a few species that I have bred and always had success with even if there was a great difference of temperature or water quality. I never had a batch of newly hatched fry die off for this reason. I already had raised some common young Corydoras this way and had good success. Strange as people sometimes try different things with harder species, instead of sticking to the good old method.
Fuller, Ian. Breeding Corydoradine Catfishes, 2001. Pages 125-127
There is further information on this species on the Cat-eLog page.
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