An organic complement for fertilizing vegetable species, as an organic product which fulfills with the features of a growth stimulator, mainly manufactured from green algae (Ulva rigida) and brownish algae (Macrocystis pyrifera). The invention includes a process for obtaining the complement that requires washing, grinding, acid and alkaline digestion, filtering and packaging steps. The most important used supplies are hydrochloric and phosphoric acid, and potassium carbonate. The product allows to improve the absorption efficiency of the nutrients supplied by the fertilizers, guaranteeing an optimal growth for the plant species, achieving a higher production in a short period of time. The product is biodegradable and beneficial for soils.