4
MAINTAINING FISHES
The presence of fishes increases the dissolved salt
content of water and alters the composition of its ionic
system. The effect of this change on fishes is not
known. Short of pollution, fishes alter water in such a
manner as results in iacreased growth of other fishes
subsequently occupying it. This phenonemon is
known as conditioning.
Fishes can be crowded to the extent that both reproduction and growth are inhibited. Exactly what
these inhibiting substances are is not known. The
situation may be nothing more than a combination of
waste materials concentrated enough to be generally
toxic to fishes and thus interfere with all normal
functions.
Natural processes eliminate or inactivate some
waste materials. Green plants, including algae, take
up large quantities of carbon dioxide and release
oxygen. Bacteria break down fecal and unused food
materials. Snails and other invertebrates utilize excess food materials. Chemical reactions cause the
breakdown and inactivation of many wastes. Still
other wastes are lost as gases at the water's surface.
But none of the natural processes are entirely adequate when fishes are crowded beyond a certain
point. We do not presently know the range of density
values which constitute the upper limit that can be
accommodated by natural processes. In terms of
grams of fish per liter of water it is probably less than
one gram per hter in the absence of an algal bloom
or other plant growth. Higher densities appear possible when plant growth is prevalent. The relationship wiU vary with species of fish and a number of
other considerations.
Among tropical fish hobbiests the rule of thumb for
MAINTAINING FISHES
The presence of fishes increases the dissolved salt
content of water and alters the composition of its ionic
system. The effect of this change on fishes is not
known. Short of pollution, fishes alter water in such a
manner as results in iacreased growth of other fishes
subsequently occupying it. This phenonemon is
known as conditioning.
Fishes can be crowded to the extent that both reproduction and growth are inhibited. Exactly what
these inhibiting substances are is not known. The
situation may be nothing more than a combination of
waste materials concentrated enough to be generally
toxic to fishes and thus interfere with all normal
functions.
Natural processes eliminate or inactivate some
waste materials. Green plants, including algae, take
up large quantities of carbon dioxide and release
oxygen. Bacteria break down fecal and unused food
materials. Snails and other invertebrates utilize excess food materials. Chemical reactions cause the
breakdown and inactivation of many wastes. Still
other wastes are lost as gases at the water's surface.
But none of the natural processes are entirely adequate when fishes are crowded beyond a certain
point. We do not presently know the range of density
values which constitute the upper limit that can be
accommodated by natural processes. In terms of
grams of fish per liter of water it is probably less than
one gram per hter in the absence of an algal bloom
or other plant growth. Higher densities appear possible when plant growth is prevalent. The relationship wiU vary with species of fish and a number of
other considerations.
Among tropical fish hobbiests the rule of thumb for