Corydoras sterbai is a very attractive catfish which comes from the Upper Rio Guapore River in Brazil. It is often confused with Corydoras haraldschultzi which is an equally attractive fish from the same region. The experts tell us that the C. haraldschultzi has a light body and head with dark spots and lines. C. sterbai has a dark head and body with light spots and lines. It brings to mind a Zebra, white with black stripes or black with white stripes. There is a definite difference in the two fish and they are often found mixed together in store tanks or wrongly named. Over the years I have seen or heard of them being spawned by aquarists on the rare occasion, but never on a regular basis.
While at the Catfish Convention hosted by the Potomac Valley Aquarium Society in Laurel, Maryland in October 2004 I had the pleasure of meeting Ian Fuller the Corydoras catfish expert from England. During a question session with a panel of experts someone asked the question ‘at what temperature do you spawn Corydoras sterbai?’ Ian Fuller answered at 82 degrees F. That was the key and could well be the answer to other hard to spawn corys. Most of the commonly bred corys spawn in average hard tap water in the high 60’s to low 70’s as long as pH and DH are not extreme. But many beg to be different and finding the key to what triggers them is what you have to discover.
A week or two after arriving home from the convention a ten gallon tank came empty. I decided to capitalize on my newly gained knowledge. I checked my cory catch-all tank where I keep fish that I am not currently spawning or loners that I don’t know what to do with. It was in this tank that I found three C. sterbai given to me by Paul McFarlane when he downsized his fish room for health reasons. I placed the three fish in the ten gallon tank and added a heater set at 82 F.
The water was mostly from my reverse osmosis (RO) unit which is a must have for real fish breeders. The only things in the tank were a box filter and a yarn spawning mop with a float. The fish were fed well on white worms, black worms, frozen brine shrimp and frozen bloodworms. After a month or so of good conditioning it became apparent when they were viewed from above that I had two males and one female. The female was obvious because her sides bowed whereas the males’ sides were straight. Nothing much was happening other than one male would get amorous and tickle the top of the female’s head with his whiskers after a water change.
Then the day after Christmas the weather in my area changed when a low pressure front came through, and that, along with a water change the night before, set them off. I came down that morning and eggs were being laid both on the glass and in the spawning mop. They continued to spawn on and off all day. When they finally stopped I removed the eggs by rolling them off the glass with my finger and picking them from the mop. They were placed in a covered plastic container with a lid. A drop of acriflavine was added to prevent fungus and it was placed on a warm shelf near a heat duct in my fish room. The following day they laid some more eggs. At the time of spawning the temperature was 84F, the pH was 6 and the DH was 5. The eggs started to hatch on the fifth day and it was another three or four days before the fry were ready to eat microworms and live newly hatched brine shrimp. They spawned again three and a half weeks later laying another hundred or more eggs with half of them hatching. Most of the fry from the first spawning are three quarters of an inch in length and between the two spawnings I have over a hundred fry. They look like they should spawn again soon and hopefully the hatches will be even better as I noted that the hatch was greater from eggs that I rolled onto the sides of the container than the ones that lay on the bottom.