Origin: Amazon River basin
Maximum Size: Males smaller than 2 inches, females larger
Housing: 10-gallon okay. Larger better for breeding.
Security: Not necessary
Temperature: 70 to 80 ºF
Attitude: Good Natured. Eager eater.
Foods: Loves all foods – especially worms
Water: Prefers pH around neutral but very flexible
Sexing: Males pointed dorsal fin. Females rounded belly.
Corydoras means “little-armored catfish.” Cory scales protect them from some predators that snap up little swimming morsels. Their dorsal and pectoral fins also contain the so-called catfish “horns,” another protection against fish gulpers. Most people shorten their name to “cory cats” for convenience.
Lots of Species: You can usually find a good variety of species. Most people prefer the bronze corys (Corydoras aeneus), spotted corys (C. paleatus), and albino corys (probably both C. aeneus and C. paleatus). These locally raised species sell for less and do the same job as the “cooler-looking” imports.
Fun fact: Corys like to travel in packs.
Origins: The Amazon River level goes up and down with the rainfall amount. Schools of thousands of corys congregate in shallow pools left behind.
Labyrinth Breathers: Corydoras prefer to live in cooler waters but possess an auxiliary breathing organ that enables them to survive in those shallow pools of low oxygen warm water. You can see them come up to the top to breathe. If you’ve walked barefoot along a river in the summer, you know how warm these shallow pools can get.
Water Conditions: Corydoras easily adapt to a variety of clean water conditions as well as nearly any temperature – even unheated goldfish aquaria.
Corys rank among the easiest fishes to keep. They stay small. They sport cute little whiskers. They roll their eyes occasionally. They interact with each other when kept in herds. Corydoras make excellent scavengers, but they are also good looking fish. And the different species provide a variety of color patterns.
Size and Sexing: Corydoras top out at two inches. Mature females grow longer (and wider) than the males. The rounded belly of the female keeps her nose off the gravel when she rests. They usually take two years to attain breeding size, but some breed earlier. Corys live several years.
Jumpers: Not usually thought of as jumpers, corydoras can leap out when going to the top for air. It happens most often where your filter stems release their bubbles. Their armored plates and air-breathing abilities enable them to live quite awhile on the floor. We still prefer keeping ours wet.
Beware Large Goldfish. Small corydoras mix poorly with large goldfish. Big goldfishes try to swallow small corys. The cory’s “horns” stick in the goldfish’s mouth. The cory drowns. You have to extract the cory with longnose pliers or your goldfish could die also.
Foods: Corys eagerly eat whatever you feed them, but don’t expect them to clean up your overfeeding mistakes. They will not eat old, spoiled food growing mold on the bottom. Use snails to clean up any nasty food on the bottom. Corys love live California blackworms.
Fry Foods: Weirdly enough, corydoras catlets do best in tanks with a little gravel sprinkled on the bottom. Best first foods include micro worms and newly hatched brine shrimp – even the frozen. You can see baby albino cory bellies turn orange when they eat brine shrimp. Use a sponge filter. They need clean water.
I have a pattern that I use to spawn them. I keep them in warm water around 75 Fahrenheit for about 6-8 months, keeping them with a consistent diet of flakes, then bloodworms once every two weeks. During that time I change about half the water every two weeks as well. After the 6-8 months is done I do a full water change and remove the heater and lower the temperature down to about 68F. During this period I feed them three times a day instead of two and I feed them a mix of bloodworms, flakes and some brine shrimp. They usually spawn in this period. So far I have successfully incubated and raised 4 batches of cory eggs (about 200-300 laid, about 100 fungi over, about 50-80 fry keel over and die.. then the rest survive.
To increase your live egg %, add methylene blue. Hatch the eggs in a bare tank with a bit of gravel on the bottom and start them on micro worms or newly hatched shrimp (hatched daily). You’ll get more survivors.