In Cameroon, the principal objective set out for the aquaculture sector is to sustainably improve farmer incomes. To be profitable and sustainable investments in aquaculture businesses need to achieve a scale sufficient to allow for the purchase of inputs, the hiring of labour and the marketing of outputs for cash income. At present, political instability and poor governance in many African countries mitigate in favour of very large-scale farms that can absorb risk. However, within the range of possible scales, small and medium enterprises generate more employment and equitable economic growth than large scale investments. Participatory, on farm, action research in Cameroon has elaborated a tool, the Aquaculture Business Planning Assistant, that can help governments and smaller investors identify the basic production system that can achieve a minimum profitble scale.