Use of bioassay CG (Colour Graduation) to determine density of Skeletonema sp. at hatchery

The natural food that is often used in hatcheries is Skeletonema sp. Phytoplankton provision of Skeletonema sp. on fish larvae or seeds carried out in hatcheries tend to be based on estimates and experiences while in the field. This study aims to obtain indicators that can be used in estimating the range of cell density of Skeletonema sp. just by looking at the Bioassay CG (Colour Graduation) kit. This research was conducted at the CV. Puncak Sinunggal, Barru Regency. In this study, researchers use a black CG Bioassay prototype in the form of a box equipped with LED lights, batteries, a colour indicator paper kit, 150 mL glass beaker, and a power button. Samples were observed in the exponential phase or 24 hours after the inoculation was diluted by adding culture media to obtain several different colour gradations. The dilution carried out is mixing between samples with culture media with each ratio, beaker glass (BG)1 (10: 0); BG 2 (9: 1); BG 3 (8: 2); BG 4 (7: 3); BG 5 (6: 4); BG 6 (5: 5); BG 7 (4: 6); BG 8 (3: 7); BG 9 (2: 8) and BG 10 (1: 9). Each treatment was carried out three replications and assisted by 9 panelists. The results showed 10 different colour Skeletonema sp. cell density increases with colour change, where the lowest range is in the S10 colour with density 38-75×104 cells.mL-1 and the highest in S1 colour with a density of 612-740×104 cells.mL-1.