A Classification of the Biological States of
Waters and of Fish-holding
Procedures
FISHES ALTER the watei in which they live. They
remove dissolved oxygen and contaminate the water
with fecal, respiratory, and urinary wastes. When
fishes are fed nonliving food, the water is further
contaminated by soluble components of the food as
well as any uneaten portion of nonsoluble constituents. There is, of course, a direct relationship between the degree of crowding of the fishes and the
extent to which the water is contaminated or altered.
The different contaminants affect the water in different ways. Fecal and imutilized food materials
cause the water to become turbid, cause a build-up of
carbon dioxide and ammonia, and increase the number of decay organisms, especially bacteria. If unusually abundant, these organisms can seriously
reduce the dissolved oxygen content. Some of the
saprophytes such as the water molds Saprolegnia spp,
may become parasitic on the fishes or their eggs.