This paper reviews existing knowledge concerning the outputs of tropical aquaculture production and the environmental capacity of a range of coastal ecosystems, including mangroves, seagrass, coral reefs and exposed shores. Some preliminary rules of thumb are presented for estimating environmental capacity in relation to tropical coastal aquaculture and agriculture, and the various models which may be used to assess more accurately the capacity in particular locations are also discussed. The way in which these estimates may be used in the planning and management of aquaculture development is considered. Particular attention is paid to the issue of “allocation” of environmental capacity to different users or activities.