Tilapia, Oreochromis niloticus, feeding on a microbial matecosystem dominated by the cyanobacteriim, Oscillatoria, grew faster than control tilapia fed at 3% of their body weight per day. This has been shown in previous experiments where ensiled grass stimulated a bacterial and cyanobacterial (blue-green algae) bloom on the water surface. The objective here was to develop a management system using a novel laboratory tank and field pond design which permits the microbial mat ecosystem to develop in the presences of grazing tilapia.