The requirement of live microalgae as a food source for larval stages represents a significant challenge for bivalve hatchery operations. The cost of live microalgae production represents 30- 50% of operation cost for a bivalve hatchery. The requirement for multiple species and contamination/culture crash of live microalgae poses an additional challenge to hatchery operations. To assess the efficacy of an alternative diet , commercially available microalgae concentrates were evaluated as a partial or complete replacement to live microalgae for culture of the hard clam, Mercenaria mercenaria , larvae. Larvae were fed one of six diets from 2-14 days post fertilization and growth, development and survival were assessed as response variables. Larvae fed a live microalgae diet performed better than those fed partial or complete replaced diets . Larvae fed partial and complete replaced diets were significantly smaller than those fed live microalgae. Foot development was significantly delayed in those fed complete replacement diets compared to partial replaced or live microalgae diets . Although survival at 5 days post fertilization (DPF) was similar among the dietary treatments , survival at 14 DPF varied significantly (Table 1) . These results suggest that replacing live microalgae with a microalgae concentrate is likely to affect growth, development, and survival. However, live microalgae may be replaced partially for a short duration without affecting production performance.