Water hyacinth is wild plant that grows very fast. Its existence which covers the waters can disrupt irrigation, water transportation until cause flooding. To control this plant growth, grass carp fish, which are herbivorous fish, are chosen as natural predators. The interaction between water hyacinth and grass carp fish is modeled in the prey predator system with harvesting of both. The provision alternative food aims to meet the needs of grass carp’s food, but its costs need to be minimized. The optimal control problem is applied to determine amount of alternative food provision and harvestig rate so it can minimize the cost of providing alternative food, harvesting rate and population of water hyacinth and maximize harvesting rate and population of grass carp. The solution is obtained by applying the pontryagin principle and runge kutta forward backward sweep methods. Simulations are performed to capture an optimal solution.