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At the November 2003 D.R.A.S. auction I bought a bag of six Corydoras paleatus, commonly known in the fish hobby as the “Salt and Pepper Cory”. Unfortunately, at different points in time during the next year, I lost four. Fortunately, the two surviving Corys turned out to be a breeding pair. I didn’t know how old the pair was, but the female was a good 3.5” in length and full bodied. The male was probably two inches. Females are naturally larger than the males and their dorsal fins are a bit more rounded and tapered. The male dorsal fin is steeper and narrower. I kept my pair of Corys in a bare 10 gallon tank with a corner filter. The pH was about 8; the hardness was over 10. Many breeders breed several pairs in one tank to increase chances of success. Since I was left with only one pair, I had to hope they would do well on their own. My first attempts at breeding these fish occurred in the spring of 2004. I was able to get eggs twice, but none of them developed into anything except clear eggs or fungus filled eggs. I wasn’t sure what my problem was, but I did read that sometimes males may not be sexually mature. The books suggested that the keeper wait for another year. In April of this year, I tried to breed my Corys again. In the months leading up to the breeding attempts I fed them heavily on baby brine shrimp and Nutra Fin Pellets. I found the live foods to be much better than the manufactured ones. No matter how much brine shrimp I fed they always cleaned it up. With the pellets, there always seemed to be some left over. I always suctioned out the extra to avoid spoilage. In order to stimulate breeding, I continued heavy feeding and began performing daily water changes of 20-30% in the evenings. I also turned the heater off in the evenings. The usual temperature in the Cory tank was 74 degree F, but it dropped 6-8 degrees overnight. The water changes and temperature decreases supposedly mimiced the conditions of the Cory breeding season where heavy rains bring plentiful food supplies, lots of fresh water, and lower temperatures. I repeated this pattern and on the fourth day breeding occurred. The courtship ritual is truly unique. The male chases the female vigourously around the tank, mouthing her head whenever he catches up to her. Soon they settle down. The male presents himself to the female and she pushes her head into the male’s ventral area. The theory is that the male is expressing his milt. At this point, the female has several eggs cupped into her ventral fins. Once the “T” encounter is over the female floats to one side, almost as if she is paralyzed, for about 45 seconds. Then, as if she’s awakened from a trance, the female swims in frenzied fashion up and down the sides of the tank, frantically mouthing the glass, searching for a site to deposit her eggs. After a search that lasts anywhere from 45-60 seconds, she presses her pelvis into the glass, laying the adhesive eggs on the sides of the tank. Even during the laying process, the male devotedly follows his mate. Once the eggs are dropped, the pair rest for a brief period of time before repeating the same process again. At the end of the first day of breeding the pair had laid over 260 eggs. I moved the pair into an adjoining tank to protect the first batch of eggs. The next day I noticed that the pair had filled their second tank with eggs as well. Unfortunately, I did not have any other tanks available. Before I was able to remove the eggs, all but 12 became Corydoras caviar. On day three I noticed that 22 of the eggs started to darken. On day four, 2 of the eggs had small tails. On day five, there were four small, tad-pole like swimmers moving around the bottom of the tank. By day six 12 of the eggs had hatched, and by the next day I counted 20 fry. Two of the eggs with tails died. Each day through this incubation process I performed 10% water changes. Since the fry swim with a yolk sack I did not feed them the first two days after hatching, but then I began to feed them microworms twice daily. By day 10 some of the fry reached a length of ¼”. The bodies began to become spotty and I could see tiny, hair-like whiskers around the mouth. At this point I lost two more fry. To this day, 18 are still surviving. On day 12 I began feeding baby brine shrimp. On this diet it’s easy to tell when the babies are well fed because they have rounded orange bellies. By day 15 the pectoral fins are developing more distinctly and the fry are very active in their swimming. By 30 days, the fry really look like little copies of their parents. At six weeks, the fry show beautiful colouration with the dark spots contrasting with the lighter background. Many of the young have developed four barbells. Some fry at this point have reached 5/8” of an inch long. As of 8 weeks, all 18 fry are still alive, although there is a noticeable size difference among some of them, with a few much smaller than the others. I wonder if this is an early indication of gender differences. The Corydoras paleatus is a good fish for beginners. If you can replicate their spawning triggers, they’ll probably reward you with fry.
Article Source: http://www.articlefishtalk.com
David Fischer (reprinted from the September 2005 issue of 'tank talk') www.dras.ca/index.html
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