Although the hatching of Artemia cysts is basically very simple, several parameters need to be taken into consideration for successful hatching of kilogram quantities of cysts, as is needed on a daily basis in large hatcheries. The best hatching results are achieved with containers with a conical bottom, aerated from the bottom with air lines. Cylindrical or square-bottomed tanks will have dead spots in which Artemia cysts and nauplii will accumulate and suffer from depletion of oxygen. The aeration intensity must be sufficient to maintain oxygen levels above 2 mg/l, preferably 5 mg/l. The temperature of the seawater is preferentially kept in the range of 25 to 28^°C. The pH must remain around 8 during the hatching process. If needed, the buffer capacity of the water is increased by adding 1 g NaHCO₃/l (this is particularly needed when hatching at salinities lower than 30 ppt; the minimal required salinity is 5 ppt). Cyst densities may be as high as 5 g/l for small volumes (<20 l), but should be decreased to a maximum of 2 g/l for large volumes (> 100 l). Artemia cyst shells may be loaded with germs of bacteria and fungi. These may be removed by disinfection using bleach. Strong illumination (about 2000 lx at the water surface) is essential, at least during the first hours after complete hydration, in order to trigger the start of the hatching mechanism (Dhont et al.,1993).

After hatching and prior to feeding the nauplii to shrimp larvae, the nauplii should be separated from empty cyst shells, unhatched cysts, debris, microorganisms, and hatching metabolites. Five to 10 min after the aeration is switched off, cyst shells will float, while nauplii and unhatched cysts will concentrate at the bottom. Since nauplii are positively phototactic, their concentration can be improved by shading the upper part of the hatching tank and focusing a light source on the bottom. First, unhatched cysts and other debris that have accumulated underneath the nauplii are siphoned or drained off. Then the nauplii are collected on a submerged fine-mesh screen (< 150 µm) and rinsed thoroughly with tap water in order to remove possible contaminants and hatching metabolites such as glycerol (Dhont et al.,1993).

Nauplii can also be harvested with a concentrator-rinser, a device especially developed for good rinsing of the nauplii (Dhont et al.,1993).