The larvae of clam Meretrix lyrata at swimming stage (D-veliger) were reared until Post-metamorphosis stage, called crawl larvae that ready to become spat. Two experiments were conducted as follow: 1/ The experiment on rearing clam larvae at diffrent stocking densities such as 5, 10 and 15 larvae per ml and 2/ The experiment on rearing crowled larvae of clam in different substrate such as clay, sand, scallop powder and tank bottom (bare substrate). The experiments were conducted in 100 litter cylinders in the hatchery in June 2010.