Fully anaerobic, methanogenic digestion of aquaculture sludge has been reported by several authors (reviewed by Mirzoyan et al., 2010). Although operational conditions differ considerably among the few studies conducted, it can be concluded that a considerable
degradation and stabilization of aquaculture sludge can be achieved through methanogenic digestion. Issues such as inhibition of the methanogenic activity by unionized ammonia concentrations due to low C/N ratios of the sludge, optimal dry weight content of the sludge, and optimal hydraulic retention times of the methanogenic reactors, still require further investigation prior to the full scale use of these systems.