Formal accounting sheets usually turn out being inadequate to identify the technical or managerial elements causing the financial situation of an enterprise and to imagine the future of that enterprise as well. That is the reason why, as it has been widely developed in agriculture, a techno-economic approach linking the physical flows related to the activity of the enterprise and the resulting financial flows should be a better answer to the need of vigilance on husbandry practices and to the need of projection in the future. The realization of a computerized simulation tool taking into account some relevant technical, biological and economic criteria makes it possible to assess the consequences of investment decisions on the cash-flow and on the viability of an enterprise. This method has been applied to the case of a Greek sea-bass farm which has decided to build a hatchery.