Local production of mixed sex Nile tilapia in irrigated rice fields has been introduced, established and then spread through farmer-to farmer contact in Northwest Bangladesh benefiting poor households in a number of ways. Food fish farmers have improved access to high quality seed at the time of peak demand early in the monsoon season. The seed producers benefit through small but strategic cash flows but also improved production of their fish for their own consumption, both as large fingerlings and fish after further grow on. A range of social benefits emerged during qualitative assessments. Initially introduced through onfarm research and then Farmer Field Schools' adopters starting with common carp and Nile tilapia have adapted the basic concept, tending to expand to a certain level and increasing the number of species produced. Difficulty in delivery of sufficient quality broodfish to rural areas is a major impediment to broader adoption of decentralised production, Capacity among local promoters to support initial broodfish and knowledge supply was important to the development of decentralised seed networks. Confusion over the perceived qualities and constraints of mixed and mono-sex tilapias respectively can undermine acceptance of decentralised seed production strategies among policy makers.