You know your cory catfish is dying if it displays the following signs of poor health:
- Weakness and lethargy
- Slow swimming, or none at all
- Upside down swimming
- Refusal to eat
- Gill discoloration
- Troubled breathing, gasping at the surface
- Clouded and bulging eyes
- White spots on the body
- Cloudy mucus covering the body
Your cory catfish may be exhibiting these symptoms due to an improper acclimatization process, water temperature or pH changes, poor sanitation, water poisoning, or self-poisoning due to stress.
To prevent your corys from dying, keep them in groups, feed them a healthy diet, maintain the tank regularly, and keep them away from aggressive tank mates.