Abstract. One of the alternatives to overcome and control bacterial V.
Harveyi disease in fish culture without environtmental disturbance is the use
of brown macroalgae containing antibacterial natural material and possessing
potential as antibacterial. This study was intended to find asafer and
environmental friendly method of bacterial disease control in fish culture and
discover antibacterial active compound in vitro based on solvent polarity level
and in vivo test of brown macroalgal active extract that can be applied to
increase the fish survival from bacterial disease in fish culture. Methanol
extraction is capable of producing the highest crude extract of all seaweeds.
It is true since the highest rendemen produced is that using the methanol
solvent. All extract had ability to inhibit the bacteria A.hydrophila.
Qualitative test on various brown seaweed species revealed that all brown
seaweeds contained phenols, flavonoid, steroid, and tannin but not saponin, so
that these compounds arepossible to develop as natural antibacterial and
immunostimulant.

Keyword : brown algae, antibacterial, Aeromonas hydrophilia, phytochemistry