Survey for microorganisms associated with the Nile tilapia fish revealed that more than 20 fungal isolates belonging to different genera and species including Saprolegnia, Trichoderma, Alternaria spp., Penicillium, Fusarium sp., Fusarium semitectum (= F. incarnatum), Cladosporium, Phoma, Nigrospora, Aspergillus niger and Aspergillus flavus in addition to five bacteria were isolated from naturally diseased fish.  In the winter season of 2002, an attempt was made to isolate Saprolegnia sp. from moderately infected fish, water, and feed sampled from the saprolegniasis-affected pond. Saprolegnia sp. was successfully recovered from the infected fish and pond water samples but was not found in the feed samples.  However, many saprophytic fungi and bacteria were found contaminating the fodder samples.  In the mid summer of 2002,  Aspergillus ochraceus was found associated with a syndrome of eye dropping on Nile tilapia appeared in ponds of a commercial intensive fish culture located in the area close to Kafr El-Sheikh governorate.  This is the first report of using the fungus Trichoderma spp. for biological control of fungal diseases of fish.