Harvest optimization of four Kappaphycus species from the Philippines

► Culture duration in four farmed Kappaphycus species was optimized with the aid of a mathematical formula to derive a weekly optimization index. ► Three key attributes of these seaweed resources, viz., seaweed biomass, carrageenan yield and gel strength, were incorporated in the optimization. ► Highest optimization index was obtained during the 8th and the 9th week of culture. ► Farmed Kappaphycus species are recommended to be harvested during these weeks in culture.