In general, herbicides should be used
only to change one type of plant community
to a more desirable type. For
example, mats of filamentous algae are
often responsible for excessively high
pH in recently filled ponds used for fry
or prawn culture. Filamentous algae are
also undesirable because they interfere
with pond management, particularly
feeding and harvest. Certain herbicides
can be used cautiously to eliminate
these algae in favor of a phytoplankton
bloom. In prawn ponds, some success
has been achieved with Hydrothol
191®. Hydrothol® appears to be safe for
juvenile prawns at an application rate of
not more than 0.2 ppm, but there is still
the danger of oxygen depletion. The
Aquaplant Web site (http://aquaplant.
tamu.edu) contains more information on
selecting and using aquatic herbicides.