we, in PSU, Thailand, have done several experiments during these years, involving fermented organisms both plants and animal esp. fishes, which have been used in producing organic Spirulina. Solution from fermented fish showed more depressive effects in growing Spirulina than those from plants. Hwoever, the sources of organic as well as the concentrations applied to the culture are very important. generally materials were fermented anaerobically in a ratio of 1: 1: 0.1 (w/v/w) (Schroeder, 2004) to get stock solution for the Spirulina culture. Fishs: Rastreeliger brachysoma, Oreochromis niloticus, Osteogeiosus militarias, Caranx S. leolepis were used. Planst: Papaya(Carica papaya), morning glories, Local banana (Musa sapientum) Asystasia gangetica etc. have been tried. It is clearly that, the more the concentration of these organic were, the the worse of growth of the Spirulina was. we have been trying to get explaination of these phenpmena...in oes concentration of less than 2%Spirulina grew quite well in such media. Culture produces very few residue after harvest compared the those eapplying chemical, although significantly less cell density was..but it peak sig faster, easy and very cheap...the most important is environmentally friendfly.
there was a literature explaining the similar happening to blue-green algae in rice field but very un specific.
the word...allelopathy...is new for me..but it seems to be the way out for our problem..even beginning.