The O. niloticus which injected experimentally by
intrapretonial inoculation with P. anguilliseptica and
treated by 0.5 ml of A. wisconsinense methanolic extract
showed mortality 12.5%, while experimental injection of
P. anguilliseptica without treatment gave mortality 50%.
This means that the algal extracts was active in vitro and
in vivo. Austin et al. (1992) indicated that extracts derived
from Tetraselmis suecica inhibited Aeromonas hydrophila,
A. salmonicida, Vibrio anguillarum and V. salmonicida in
vitro. The proper management is essential to success of
aquaculture operations, while the inadequate management
is the principle factor in triggering disease outbreaks
(Austin and Austin, 1993; Plumb, 1999).