Eucheuma denticulatum is one type of Rhodophyceae (red algal) which produce iota carageenan fraction. Iota carageenan is the most stable carageenan in acidic solution and form a strong gel in a solution with salinity. E. denticulatum also known as E. spinosum which has cylindrical thallus with braching thallus taper and or blunt tipped , overgrown by so many nodules arranged regularly rotates around the branches, much more than E. cottonii. This one species can be found in a variety of shades from brown to red, especially when cultivated. The planting period is one of the critical success factors for farming activities. Planting only in the right season reduces the risk of crop failure. The waters of  Tomini Bay are potential for seaweed farming, including E. denticulatumi species. Limited information on the optimal planting period cause less maximal production of E. denticulatum. This study aimed to obtain an information about the planting period of E. denticulatum in the waters of Tomini Bay, Gorontalo Province, Indonesia.

A full year study conducted in 2015 in the waters of Tomini Bay, Gorontalo Province, Indonesia by cultivating E. denticulatum applying long-line method. A weighed seed of 50 g were tide up into a rope with 15 cm space between clumps then assembled in 35x10 m construction. Cultivation process done for seven cycle with a maintainance time were 45 days per cycle. Daily growth rate observed by weighing the cultivated seaweed once per cycle. To support the cultivation process, some parameters of water quality were measured once a week, physically and chemically. Maintainance also done by controlling the epiphytes material, moss, and biofouling which could affect the thallus. The result showed that the best productive planting period was in fifth cycle that is between August to September in dry season. E. denticulatum is the species which is not like lower salinity in rainy season. Highest DGR reached to 4,76% in fifth cycle. Pay attention to this productive planting period reduces the risk of crop failure that were a spooky thing for the farmer.