This document defines and describes diseases in organisms. It notes that diseases are abnormal symptoms or activities in organisms that are in disadvantageous conditions. Diseases can be infectious or non-infectious, with non-infectious diseases including those related to nutrition, water quality, or toxins. Infectious diseases are caused by smaller organisms like bacteria, fungi, protozoa, or parasites. The document also lists specific causes and examples of nutrition-related, water quality-related, and toxic-related diseases.

2.  Abnormal symptom/activity showing by an
organism/ population in which the organism
is/are in disadvantage condition.

3.  Disease
 Infectious Diseases
 Non Infectious Disease
 Nutrition related Disease
 Water quality related Disease
 Toxic related Disease

4.  Causing by an organism or group of organism.
 The organisms is/are smaller than host.
 Causal agent;
 Bacteria
 Fungi
 Protozoa
 Parasites
 Etc.

5.  Nutrition related Disease
 Protein and carbohydrate deficiency
 Vitamin deficiency
 Water quality related Disease
 Dissolved Oxygen
 Ammonia
 Nitrite
 pH, temperature, salinity,
 Toxic related Disease
 Pesticide; insecticides, herbicides etc.

6.  Space Competition
 Nutrient Competition
 Extra Metabolite Inhibition
 Immune Stimulation (Immunostimulant)
 Water Quality Maintenance

7. Space Competition

8. Nutrient Competition

9.  Extra Metabolite Inhibition

10. Immune Stimulation (Immunostimulant)

11. Water Quality Maintenance