The Effect of Sargassum Extract on Culture Medium to The Growth of Chaetoceros gracilis

Hatchery is one of important factor s to maximize shrimp production. O ne of supporting factor s is the availability of qualified natural foods in sufficient quantities. The aim of this study was to know the addition effect of extract S argassum to culture medium for population growth of Chaetoceros gra c ilis . C ulture medium  used for microalgae C. grasilis was a 12 liter jar with density of 10 5 cell/m L . The Sargassum extract was obtained by processing S argassum waste through anaerob fermentation, then was extracted and considered as liquid organic fertilizer . Tested treatment was A = 0 ppm (without Sargassum extract ), B = 10 ppm of Sargassum extract , C = 20 ppm of Sargassum extract and D =30 ppm of Sargassum extract for three replications. It was found that the population density of C . gracilis increase d and the highest algae density occurred i n treatment D on day 5, followed with C, B and A, which were 353,433 cell/mL, 336,833 cell/mL, 308,867 cell/mL and 244,433 cell/mL . This illustrates that the addition of high doses has affect ed the population density of microalgae C. gracilis .