slurry followed by pressing to further reduce the water content produces a compressed cake of phytoplankton which is easy to manipulate microfiltration is the preferred method of harvesting cultured phytoplankton apparatus for centrifugation and microfiltration of phytoplankton can be obtained from for example u s filter co warrandale pa the collected phytoplankton is then placed in plastic bags and frozen for a maximum of 30 days when a pond needs to be seeded with phytoplankton the phytoplankton is taken from the freezer in the early morning and deposited in the designated pond in an evenly dispersed pattern growth of phytoplankton in the ponds 17 is fostered by the addition of nitrate and phosphate fertilizers the amount of fertilizers added varies by season in the summer season from june to november between about 6 6 to about 17 6 lbs per hectare of pond size nitrogen containing fertilizer typically urea is added when the ponds 17 are seeded with phytoplankton between about 3 3 and 11 lbs per hectare of pond size phosphorous containing fertilizer is also added to each pond 17 at the time of phytoplankton seeding subsequently in order to maintain growth between about 2 2 lbs to 11 lbs per hectare of nitrogen containing fertilizer is added weekly to each pond 17 phosphorous containing fertilizer is added weekly at a rate of 1 1 lbs per hectare to 8 8 lbs per hectare in the winter season.