Whether the seawater for seedling cultivation must be pretreated depends on the water quality of the water source, which mainly refers to the indicators such as diseases, red tides, pollution and turbidity of the water source. There are three kinds of commonly used water treatment methods, namely physical method, chemical method and biological method.

(1) Physical treatment

There are sand filtration, activated carbon filtration, dark precipitation and alum precipitation.

(2) chemical treatment

bleaching powder, chlorine dioxide, ozone and other treatment methods are used. The seawater treated by the above methods must be fully aerated or dechlorinated with sodium thiosulfate before use.

(3) biological method

At present, biofilm treatment is widely used to effectively remove ammonia nitrogen and nitrite from water.