Fish disease management is a critical practical skill for every aquaculture practitioner. Outbreak events caused by viruses, bacteria, fungi, or parasites are frequently triggered by avoidable environmental stressors such as poor water quality, overcrowding, and suboptimal nutrition. This article provides a field-oriented guide to recognizing the warning signs of disease, understanding the conditions that predispose fish to illness, and implementing prompt preventive and treatment responses. Using clear descriptions, practical tables, and evidence-based recommendations, this guide equips fish farmers, hatchery managers, and extension workers with the foundational knowledge needed to minimize disease-related mortality and economic loss. The article emphasizes that early detection, routine pond hygiene, and judicious use of permitted therapeutics are the three pillars of effective fish health management.