PROBLEM TO BE SOLVED: To provide a method for removing various algae such as diatoms by carrying out washing of laver or a laver net at a relatively high pH by using a treating liquid containing no or a remarkably reduced amount of an organic acid or an organic substance adversely affecting the natural environment in culturing the laver. SOLUTION: An acid solution containing an inorganic oxide, an inorganic peroxide, ferric chloride or ferric sulfate is diluted with seawater and regulated to pH 2-2.5. The resultant regulated solution is then brought into contact the laver or laver net.
