High levels of ammonia, nitrate, nitrite or pH concentrations are common reasons why cory catfish die, according to veterinary doctors Foster and Smith. Other common causes of death include unregulated aquarium water temperature, infrequent cleaning and the eating of spoiled food as a result of overfeeding.
Cory catfish are considered a hardy breed that remain small in adulthood and do not require a large tank. Cories clean up the aquarium substrate, keeping the bottom of the tank clean and maintaining water quality. The ideal aquarium conditions for this breed are temperatures between 68 to 78 degrees Fahrenheit, a pH of 6.2 to 7.2 and a KH of 5 to 18. The use of pH-regulating pellets or wafers, an automatic aquarium water changer, an aquarium heater adjusted to the above temperature range and an exterior power filter, such as the BIO-Wheel, maintains the ideal cory living conditions.
The bottom of a cory catfish tank should be covered with a maximum of 1/4 inch of gravel. Because Cories are a voracious breed of fish and eat most organic matter found at the bottom of tanks, overfeeding should be avoided. Remaining food particles sink to the bottom and spoil, causing sickness when eventually ingested.