They are grown in a semi-controlled environment with the use of upwellers. Seed Quahogs are placed in round silo containers and water is actively forced through them in order to deliver phytoplankton to the growing clams.
Clams are filter feeders and thus trap and filter out their food as the water passes by.
Success of an upweller system is due in part to several environmental factors which can be monitored and correlated to growth in the nursery. Environmental factors which effect quahog seed growth include, but are not limited to, water temperature, salinity, and dissolved oxygen. Quahog embryos develop optimally at 27.5 ppt and early-stage larvae cannot develop below 17 ppt. The upper salinity limit for Mercenaria is 35 ppt. Also, the clams are rinsed daily with freshwater to clean the silos and tanks.