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Seawater can be drawn directly from the sea or from a sump pit. If the course of the water is relatively clear, the water can be pumped directly into the overhead filter tank and stored in the reservoir or storage tank. Water is then gravity-fed to various culture tanks through its delivery pipes. However, it the water is turbid and contains a high concentration of suspended solids, the water is pumped first into a sedimentation tank where the suspended solids are allowed to settle down and the clearer water on the top is pumped into the filter tank. Water can also be filtered with high pressure sand filters. Sometimes when the water source is far from the shore due to low tide and if large quantity of water is needed continuously, the intake pipe should be laid horizontally from the littoral zone to the underground sump pit and the filter tank. Whenever possible, the seawater should be drawn directly from a tube well. Water from the tube well is usually clear; and if clean water is needed, it can be pumped directly into the filter tank (Kungvankij et al., 1986).
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