Brightwell Aquatics PhytoGold-M, 8-20 Micron phytoplankton Suspension for Soft Corals, Clams, sponges, Other Filter-feeders, 2 Liter 8 - 20m Phytoplankton Suspension for Soft Corals, Clams, Sponges, and Other Filter-Feeders Ideally-sized for many soft corals, clams, sponges, tunicates, tube worms, and larval invertebrates. Formulated to provide over 50-million phytoplankton cells per ml. Does not require refrigeration.