The research programme on aquacultural treatment of nightsoil has been conducted at the Asian Institute of Technology (AIT) for about 10 years. This paper emphasizes only the research scheme in which nightsoil is fed directly into single-stage, non-flow-through ponds for the production of algae and fish Tilapia (Qreochromisniloticus). The culture of herbivorous fish such as Tilapia in the same pond to graze on the algae is practical, in order to produce the fish protein biomass which is easily harvestable for animal (or human) food.
Dynamic and empirical models describing the performance of nightsoil-fed fish ponds were developed to simulate the temporal changes of various physico-chemical and biological parameters including dissolved oxygen, carbon dioxide, bacteria, algae, and fish growth. These models were based on the basic mechanisms and phenomena occurring in the ponds, and the simulated results calculated from the Continuous System Modelling Programme (CSMP) computer package available at the AIT Regional Computer Center.