A hydroponic mat (1) according to the present invention includes: a resin foam (3) containing Zn, which is an essential micronutrient necessary for growth of plants, in the form of 5 citric acid-soluble ZnO particles (2) (zinc oxide). The ZnO particles (2) have an average particle size within a range (not less than 0.02 mm and not greater than 0.7 mm) that causes scattering for the wavelength of light that chlorophyll of algae absorbs. The content of the ZnO particles (2) in the resin form 10 (3) is not less than 4.5 mg/piece and not greater than 15.0 mg/piece.
