Good and bad classification of stinging catfish ( Heteropneustes fossilis).

Good quality stinging catfish

Eyes clear and bulging
Skin shiny with natural slime
Flesh firm and elastic
Gills bright red or pink
Fresh, mild fishy smell
No discoloration or spots
Active movement if live

Bad quality stinging catfish

Eyes sunken and cloudy
Skin dull, sticky, excess slime
Flesh soft, leaves finger mark
Gills brown, grey, or black
Strong foul or ammonia smell
Presence of spots, wounds, or parasites
Lethargic or dead for long time

Conclusion
Good fish is fresh, firm, and odorless. Bad fish shows spoilage signs and is unsafe for consumption.