There are few studies with L. vannamei hatchery. Some guides suggest the stock densities varying from 100 to 150 nauplii/L (FAO, 2003). Some scientific studies used similar 150 nauplii/L densities for hatchery (Rodríguez et al., 2007). In the present study we used from 200 to 350 mysis 1 per liter of water. Since we start with mysis 1 and considering losses in metamorphosis from nauplii, passing through three zoea phases to mysis, if we had started in nauplii we infer that possibly higher densities (from 10 to 20%) could be consider for nauplii stocking. Initially, we thought to stock each experimental unit in the nauplii 5 stage, and start fertilization in mysis 1. However, starting in mysis we avoid initial error associ- ated with different stock densities, since each tank probably would present different survival until mysis 1.