We review piloted co-culture experiments of the sea cucumber Holothuria scabra with different seaweed species in existing lagoon-based seaweed farms in Tanzania during 2011-2014. Key questions were whether stocking densities would influence growth rates of both species, and whether deposit feeders would modify organic components in the sediments. From a social perspective, we investigate if local people are readily willing to become involved in sea cucumber farming as an optional livelihood. Seaweed-specific growth rates between 0.32 and 4.1 %d−1 were reported, showing significantly higher values for those treatments combined with sea cucumbers than for the seaweed monoculture (F3,1=3.20, p<0.05) at Zanzibar sites. Sea cucumber growth rates ranged from 0.14 to 1.6 gd-1, and all of the studies showed that the treatments holding H. scabra at a low stocking density (average of 130 gm-2) presented a higher growth performance than when it was stocked at more than 200 gm-2. Total organic matter in sediments increased in all treatments over the sampling periods (p<0.05). Some 88 percent of the surveyed local people showed willingness to participate in this type of mariculture for livelihood. The survey identified theft and lack of credit as the main hindrances for this activity. H. scabra is viable for lagoon co-culture with seaweed when taking into account proper stocking density, implications on total organic matter and total organic carbon in the system, and local acceptance by local people.