Native agar gels extracted from Gracilaria debilis and G. salicornia harvested during the rainy and dry seasons, were assessed for culturing the microorganisms Micrococcus luteus, Saccharomyces cerevisiae and Pleurotus flabellatus. Agars extracted from plants harvested during the rainy season were suitable for culturing bacteria, and yeast cells using the ‘Pour Plate’ method, and for mushroom tissue culture. Agar extracted from G. debilis harvested during the dry season could be used for culturing bacterial cells by the ‘Spreading and Streaking’ method. The potential for laboratory applications and for mushroom spawn production using agar extracted from Tanzanian seaweeds is discussed.