PROBLEM TO BE SOLVED: To provide a method for stably supplying iron fulvic acid required for plankton growth to environmental water. SOLUTION: At least one set of plankton breeding material composed of a mesh container filled with granular iron material, granular carbon material and adsorbent material and at least one small box of mesh container containing mulch is laminated to form a larger mesh container. The plankton breeding apparatus stored in the above is placed in environmental water, and the iron material and the carbon material are intermittently contacted in the mesh container by the flow of the environmental water to generate iron ions, and the iron ions are With the production of iron fulvic acid for growing plankton by the action of the mulch, the iron fulvic acid is adsorbed on the adsorbent, and the fulvic acid iron and the adsorbent produced by the action of the iron ions and mulch The adsorbed iron fulvic acid is continuously supplied to environmental water for a long time. [Selection diagram] Figure 1【課題】プランクトン増殖に必要なフルボ酸鉄を安定して環境水に供給する方法を提供する。【解決手段】粒状の鉄材と粒状の炭素材と吸着材とを充填した網状容器からなるプランクトン増殖材と、腐葉土の入った網状容器の小箱とを少なくとも１組積層して、さらに大きな網状容器に格納したプランクトン増殖装置を、環境水中に載置し、かかる環境水の流れで前記鉄材と前記炭素材とを前記網状容器の中で間欠的に接触させて鉄イオンを生成し、前記鉄イオンと前記腐葉土の作用でプランクトンを増殖させるためのフルボ酸鉄を生成するとともに、前記フルボ酸鉄を前記吸着材に吸着させ、前記鉄イオンと腐葉土の作用で生成したフルボ酸鉄と前記吸着材に吸着したフルボ酸鉄とを持続的に、長期間、環境水に供給する。【選択図】図１
