AT Guillard's f/2 Growth Medium 14x Concentrate, w Silica - Microalgae Feed Food for many marine microalgae species including Nannochloropsis oculata, Isochrysis galbana and others. Suitable for diatoms. Contains Silica Highest quality chemicals used in the production of this medium concentrate/fertilizer Win Monthly $100 AMEX Gift Card by simply making a purchase from Algoid Technologies. The more orders you place the more chances to win you will have. A winner for current month will be chosen in the beginning of the next month.