The pH level of ponds such as 6-9 pH relates to almost all interesting factors like temperature and even drug action. Seasonal changes and kinds of fishes relate to epidemiology. How do given climatic factors relate to disease ?

Sewage and recycling systems can be vital centers of attention. Hydrogen sulfide and other polluting gases from industries can form acid lakes. Example: Fumes from Buffalo, NY kill some of Ontario's fishes.