authorities and/or industries prior to any aquaculture
projects. Sites with no record of potential harmful species
and good water exchanges (water movement due to
tidal cycle and outside embayment) are preferable, as
turbulence may affect the growth of flagellates (White
1976) and assist in dispersal of nutrients from waste
waters.
Several other mitigation measures such as aeration
and perimeter skirting, moving pens and clay spraying
were widely practised in several countries as countermeasure to HABs events at aquaculture sites (Kim
1998; Lim 1989; rensel & Whyte 2001; Shirota 1989).
Perimeter skirting was commonly applied together with
other mitigation measure such as aeration. The skirting
(plastic sheets) creates a barrier to prevent the farm
organisms in the cages/pens to have direct contact with
the blooms. The perimeter skirting measure should also
be considered couple with management practice such as
‘stop feeding’ to avoid ammonia accumulation within
the perimeters. Fish with feed produced 3-4 times higher
ammonia than those unfed (Brett & Zala 1975).
Flocculation application as physical control of algal
blooms has been widely used in east Asian countries
(Shirota 1989). Clay is the flocculant that commonly used
to bind suspended particle (algae cells) and sink to the
bottom. Two types of clay, montmorillonite and kaolinite