An inexpensive inorganic medium for the mass cultivation of freshwater microalgae

A new and inexpensive inorganic medium (‘DS medium’) for the mass cultivation of freshwater blue-green algae (Cyanobacteria) and green algae has been developed. It consists basically of distilled or demineralized water (90%) and seawater (10%) and requires only little addition of pure purchasable chemicals (phosphate, trace elements, if necessary nitrate). No addition of macronutrients (NaCl, MgCl₂ or MgSO₄, KCl or K₂SO₄, CaCl₂) and of boron is required because they are sufficiently provided by the seawater. Decalcified water may also be suitable instead of demineralized water. For the cultivation of green algae, a higher trace element concentration is recommended than for blue-green algae. Because of its low total salt concentration the DS medium is freshwater-like. It is easy to prepare and effects rapid algal growth. It may be of special value for algal mass culture in regions which are close to the sea.