Some chemicals (e.g., potassium permanganate, formalin)
may damage fish gills or skin and should be used carefully
and only when absolutely necessary. Chemicals may also
adversely affect water quality. For example, formalin
decreases dissolved oxygen concentrations in water. Ideally,
the producer should be familiar with common health
problems, actively work to identify and treat them as they
become apparent, and seek assistance from a fish health
professional when needed.