Posted by TFH Magazine in Tropical Fish Hobbyist Blog on August 9, 2012 at 7:45 am
By Jennifer Wilkinson
Pygmy cories appreciate a well planted tank with plenty of cover. Photograph by Mark Smith.
The pygmy cory (Corydoras pygmaeus) is found in South America, but was originally discovered in the Rio Madeira system. They seem to be readily available to aquarium hobbyists at certain times of the year.
This dwarf cory can reach about an inch in length. It is a grayish brown color on the top and a lighter gray on the bottom. The two colors are divided by a dark line that runs the length of the body to the caudal peduncle. The line ends with an almost round dot on the caudal peduncle, which is surrounded in a lighter color. The rest of the caudal peduncle and fins are a clear color. The females are slightly larger than the males and especially when ready to spawn. C. pygmaeus are part of the elegans group, along with C. elegans, C. hastatus, C. undulatus, C. latus, C. guapore, C. nanus, and C. gracilis.
Pygmy cories can be found on the bottom of the aquarium, like most other cory species. However they also like to swim in midwater, about 4 inches from the bottom. They also have the capability to hover in one spot. I have kept many species of Corydoras and have found that not too many do this. If the aquarium is set up properly so that the dwarf corys are comfortable, they will be seen dashing about all day long.
If there is any motion around their aquarium or if they feel threatened they will dash off into a hiding spot. If they can’t find a hiding spot, they will come to a standstill on the bottom of the aquarium and only begin to move again when they feel the danger has passed. All the Corydoras I have kept seem to be more comfortable in an aquarium that has lots of caves, rocks, flower pots, and live and plastic plants. They seem to be more comfortable if they are under something, so providing some kind of cover is necessary. They will also dash up to the top of the aquarium to get a gulp of air.
In the aquarium they prefer to be in large groups of the same species or with other species of Corydoras of about the same size, as they are very social little fish. I usually recommend that all Corydoras be purchased in groups of three or more because of this social behavior. If at all possible, I recommend at least six, and more is definitely better with these little fish, especially in a community aquarium. In the wild these fish are found in very large groups, hundreds or thousands are not unheard of.
Bringing Them Home
I had to special order my fish from one of the pet shops I was dealing with at the time. I ordered 20 C. hastatus. When I went to pick my order up, I questioned the owner about the fish he got in. When I examined the lot, I was sure that they were not C. hastatus but C. pygmaeus. It didn’t really matter to me which one they were, as I didn’t have either one. However, the store assured me they were C. hastatus.
They were very young, approximately seven weeks old, so it was very difficult to tell just what they were. The store owner threw in two extras just in case he counted wrong. So, on the way home from the store, I wondered just what kind of fish I had and just how many I had.
When I got home I placed my tiny cories in a 20-gallon aquarium by themselves. The parameters of this aquarium were a temperature of 78°F, the pH was 7.0, and the water was soft. This aquarium was filtered with an appropriately sized external power filter with a sponge on the intake tube so these little fish wouldn’t get pulled in. Water changes were done twice a week, with about 30 percent being changed each time.
The fish were raised and conditioned on sinking wafers, several different kinds of flakes, and baby brine shrimp. After four months a few eggs were found and I was surprised to find that there was also one half-grown baby. The eggs and the one baby were moved to a 5-gallon aquarium. Two days later, all of the eggs had fungused, so I decided to move the one tiny fry back in with the adults. Unfortunately two days later he was found belly up on the bottom—he probably couldn’t handle the stress of being moved so often.
Real Breeding Attempt
Shortly after, more eggs were found. This time, after doing lots of research, I was ready to try some different techniques. What works for one hobbyist may not work for the next, so I was prepared to have many flops before actually getting a viable spawn. This time I tried suspending a net in the main tank, with a gentle flow of air bubbles under it. Then I collected the eggs with my fingers and put them gently in the net. All the eggs fungused by the next morning.
The next batch of eggs were moved into a shallow glass pan with no air stone or filter. This time they hatched, but all was lost again three days later. I believe polluted water was the cause this time. These fry are really tiny, and certainly not near big enough to eat baby brine shrimp, so a liquid fry formula was fed. Obviously way too much of this, as the water became very cloudy and a water change wasn’t done fast enough. After this I gave up for a while, or I guess you could say I took a break.
I have used this shallow glass pan method several times now with other cories and Aspidoras spp. with great success. The difference being, as soon as the fry hatch and fall to the bottom, they are transferred to larger quarters (an aquarium) to be fed. More water means less pollution. Liquid fry foods are no longer used, instead artificial plankton rotifers are used until baby brine shrimp can be fed. Lots and lots of water changes are a must. If only I would have known at the time.
Success at Last
I finally had success with these pretty little corys when I moved them into another 10-gallon aquarium down in the fishroom. They were brought into breeding condition on sinking wafers, frozen blood worms, several different kinds of flakes, and occasionally freeze-dried and frozen adult brine shrimp. The parameters of this aquarium were exactly the same as the aquarium they were in previously. For some reason there was a plastic livebearer breeder trap sitting in this aquarium. I have no idea why, as there was never a fish in it.
Anyway, this was the chosen site for the C. pygmaeus to deposit their eggs. It was covered. Unfortunately I did not witness this spawning, just found the eggs. The eggs seemed slightly smaller than those of the other Corydoras that I have raised, but developed the same way.
First a dark line appeared, and as they aged it got larger and darker, and they hatched and the fry dropped to the bottom. Their first food was artificial plankton rotifers, as they were too small to eat the baby brine shrimp. This was fed every three days, and a 30 percent water change was done every three days before the new food was added.
Water changes have to be done very carefully with a hand siphon so as not to pull the tiny fry out. This still happens, however, and most can be put back in with an eye dropper without causing them any harm. This can sometimes cause problems with broken backs or other damage, where the fry end up dying, so it is best to take it slow and easy and try not to pull them out.
After two weeks they started to eat the baby brine shrimp, so the artificial plankton rotifers were stopped. With the baby brine shrimp, 50 percent water changes were done every night. At the four to five week stage, flakes and sinking wafers were added to their diet.
These little fish had dark broken lines and looked more like C. habrosus than C. pygmaeus until they were seven weeks old. That is the time when the solid line showed up and they looked just like their parents.
Persistence Wins Out
Sometimes persistence pays off, and so does doing lots of research. However, in the end it was just some good luck and a plastic livebearer breeding trap.
These are very nice fish to add to a community aquarium, as they are so peaceful. The only problem is to remember that they can only be housed with smaller fish, such as small tetras and rasboras. I accidentally put six young angelfish in with some and let’s just say they angelfish were definitely not angels, they thought these little cories were a tasty treat. I removed them quickly to save what was left. Beginners do make mistakes—but I quickly learned from mine.