Success with a Holy Grail: Corydoras weitzmani

Author: Dr. Karel ZahrÁdka

The dedicated hobbyist/breeder, a medical doctor in his native Czech republik, details his experience spawning a rare and beautiful cory catfish.

Holy Grails

Certain fish are “holy grails”—attractive fish known from some preserved specimens and from a photo or two—that no aquarist has ever seen alive. In addition, very little is known about their natural history or aquarium care. After some time an expedition (usually German or Japanese) may rediscover the species, and it is finally brought into the hobby, and everyone goes nuts over it. Initially its price is very high, but if aquarists are able to get the fish to breed, the price typically drops after a year or two. The catfish Corydoras weitzmani is one such fish.

A Long Wait

This species was first discovered and collected by C. Kalinowski in 1949 (five specimens), but it wasn’t until 22 years later (1971) that it was described by Nijssen. Nijssen had only one new specimen, which he collected in 1969. Thus there are five paratypes, and the type locality is listed as the Vilcanota river system near Cusco in southern Peru.

The precise locality was not given—either local collectors forgot or didn’t want to reveal it. The original description noted that C. weitzmani resides at a relatively inaccessible elevation of 3350 meters (11,000 feet). Recently this information has come into question, as it frequently does with rare specimens whose locality collectors want to keep secret. (It has significance for the hobbyist, since fish from that elevation would prefer much cooler temperatures. The best information at present is that they come from lower elevations and enjoy normal aquarium temperatures.) The species was, of course, named to honor Dr. Stanley Weitzman, TFH senior consulting editor and Curator of the Division of Fishes at the National Museum of Natural History, Smithsonian Institution.

For a long time, cory lovers searched for this rare and desirable fish and tried to find its locality without any success. The half-million tourists that visited Cusco every year included many would-be collectors, even the likes of famed catfish expert Dr. David Sands, but none could find the fish. It was not until 2004 that the fish was seen alive. An expedition led by Shigezo Kamihata collected it and arranged its export to Japan in November 2004. There is a very strong interest in Corydoras catfish in Japan, and young specimens of this highly sought-after species that were only 2 cm (¾ inch) long sold for about $1000 apiece!

Instant Popularity

Hobbyists learned about the new fish in an article by Keisuke Kobayashi in the Japanese magazine Aqualife in February 2005. The original Japanese name given to them translates roughly as “dream cory,” but other names given to the fish include “Weitzman’s cory” or “two-saddled cory.” Pictures were published on the Internet, and when I saw them this species became my own number one dream fish.

The first successful breedings of this cory occurred some months later around the world, I believe by Ian Fuller in Britain, the Hoffmans and Kurt Mack in Germany, and Frank “guppyman” Flacone in the United States, among others. These spawnings sent the price spiraling downward, and today it is possible to buy specimens for about $20 to $30 each. In addition, Peruvian exporters must have discovered new collecting sites, because this initially rare species is occasionally available from them.

My Own Quest

I hunted the fish for more than a year. In January 2006 the first F1 fish I heard of were offered at a price that was high, but I was willing to pay it. What I wasn’t willing to pay was the huge freight charge from Germany to Prague of €150 ($200) for one box.

I informed many people about my quest, including my friend MiloŠ Kroupa. He works at a wholesaler and tried to import Weitzman’s cories from Peru several times. He ordered them, but they were never included in the shipments. The exporter would explain that they were out of stock. Fortunately his firm sometimes cooperates with a German importer, and in September 2006 MiloŠ called to inform me that through the German importer he had gotten a shipment of 50 wild specimens, of which 36 were alive. The price was high, but I was too near my goal to turn back; I hopped into my car and drove to the wholesaler at once.

They turned out to be adult fish and not in very good condition. I don’t like buying wild adult fish, since they could be 3 years old or 15. They can also be difficult to acclimate to life in captivity. Also, what if someone in Peru is breeding the species and shipping the spent breeders? These and other questions were tormenting me, but I produced a big chunk of cash for 10 specimens—I just couldn’t let someone else take home my dream cories!

Success at Last

On the way home my holy grails punctured the double plastic bag with their spines, and they arrived with only a small amount of water left, but they were still alive. They were quite thin, and two died during the first week, but the other eight were adapting well. I fed them well with daphnia, red worms, white worms, and tubifex, and within a few weeks they had filled out and I dared to hope for a spawning.

For the first few months the fish were not very active, but at the end of December they showed more energy and began swimming up and down the aquarium walls. They were especially active every afternoon. This continued for more than a month with no further spawning behavior. At times it looked as if they would spawn any minute, but nothing. I was frustrated and tried all the tricks—water changes, lowering the temperature, raising the temperature, feeding more live foods, artificial rain—all to no avail.

I asked my friends on the Internet forum Petfrd.com what to do. The next day I had a reply from Paul Dixon from the Bolton Aquarium: “They need tons of Java moss in the spawning tank.”

I arranged a spawning setup according to Paul’s advice, and a day later my fish spawned! It started in the late afternoon. The fish lost all their shyness and colored up nicely. The males began to chase the females, and they assumed the typical Corydoras “T” position, after which the female swims with an egg in her fins, looking for a good place to put it, which is usually in the clump of moss and only rarely on the glass. Spawning is a bit wild, and the females are chased vigorously through the Java moss. The activity stops around midnight, but even if we are not present to witness the spawning it is easy to notice the clumps of moss strewn around the tank, and the large eggs can be seen by close inspection.

Raising the Fry

Corydoras weitzmani are not egg eaters, but I prefer to collect the eggs and incubate them in another small tank. They are large, hard, and adhesive, and they can be gently collected with the fingers. It is also possible to clip the moss with scissors to harvest the eggs.

They hatch in 120 hours at 24°C (75°F). The larvae are unusually large, and three or four days later, when they have absorbed their yolk, it is necessary to start feeding them.

We can use microworms, but freshly hatched Artemia nauplii are better. The fry can also eat extremely fine prepared foods, such as powdered flakes. With heavy feeding of brine shrimp the fry will soon have golden pot bellies. With such heavy feeding three times per day, we must vacuum out all detritus a half hour after each feeding, and change one-third of the water in the tank daily using water of the same temperature and chemical parameters. Cleanliness is imperative, since the fry are very sensitive to harmful microorganisms that would otherwise flourish. These can quickly wipe out an entire batch of fry, and once they take hold it is very difficult to save any of the fish. These infections appear seasonally. I had problems with fry loss during the spring, but not during the winter.

At the age of two months the fry are 2 cm (¾ inch) long and have attained adult coloration. The best water parameters for developing eggs are a pH of about 7, GH about 3, and KH below 1. Adult fish have no special requirements in terms of water chemistry, and a temperature of 20° to 24°C (68° to 75°F) is fine.

At this time Corydoras weitzmani is still a bit expensive, but thanks to the ease with which these “holy grail” fish breed, they should be available to all cory enthusiasts in the very near future.

See the full article on TFH Digital http://www.tfhdigital.com/tfh/200712/#pg94