The global massive decline of coral-reefs ecosystem, caused by anthropogenic and natural disturbances, has been recorded in the last three decades. In response, several approaches, some of which were guided by different points of views, have discussed a variety of methodologies for the recovery of reef ecosystems worldwide. One of these approaches is based on the coral gardening concept, and employs a two-steps tactic for active restoration: (1) culturing of small coral fragments in mid-water nurseries until they reach appropriate sizes for transplantation, and (2) transplantation of farmed coral colonies into denuded reef areas. The tool-box of this active restoration concept has been studied here in Tanzania, aiming at devising appropriate restoration protocols in face of rapidly declining reef areas in the £ast Africa reef system. Two mid-water nurseries were established in September 2007 at Chumbe Island in Zanzibar and Chole Bay in Mafia Island, each holding 10,000 fragments from six spQC\Qs(Acropora formosa, A. hemprichi, A. nasuta, Millepora sp., Pocillopora verrucosa, Porites cylindrical each represented by three genotypes. The results, following a period of nine-months nursery phase, revealed interspecific significant differences in survival and growth rates for the acroporid species, Pocillopora verrucosa and Millepora sp., which showed improved outcomes when compared with Porites cylindrica. In both sites, Millepora suffered no mortality while other species exhibited low mortality ranging between 3% and 24% (per coral genotype) in Zanzibar and between 13 and 44% in Mafia Island. Coral species in Zanzibar nursery performed better in growth rates than those in Mafia; however, farmed corals in both sites were ready for transplantation within this short period of nine months. In total. 14,022 nursery farmed coral colonies were transplanted; 6912 in Changuu Zanzibar and 7110 in Kitutia, Mafia. In each site, we randomly set up 12 plots (36m2 each), of which three were transplanted with a mix of three Acropora sp. (Treatment 1, Tl), three with a mix of all six scleractinian species (T2), and six served as controls. Within one month of transplantation, an outbreak of Acanthaster planci in Changuu caused mortality at 50%. One year survival of transplants in Tl and T2 at Kitutia reached 66.4% and 62.5% respectively, significantly higher than at Changuu; an outcome recorded through species-by-species comparisons for four species (P. verrucosa, P. cylindrica, A. muricata, A. nasuta). One year following transplantation, no significant difference was documented in ecological volumes (EV) between Tl and T2 a result which is in contrast to the among species comparisons in Tl, at each site. A within treatment one-way ANOSIM comparison for fish assemblages performed between the first and last three months of the transplantation year (Kitutia reef) revealed strong separation (Tl, Global R = 0.743, P <0.001; T2, R = 0.445, P < 0.001 and T3, R = 0.694, P < 0.001) while the same treatment revealed weak separation at Changuu site Tl (R = 0.035, P >0.262) and T2 plots (R = 0.1 19, P < 0.043). Similarly, one-way ANOSIM done on the initial and last 3-month periods on invertebrates' community composition (at all sites, except Tl of Changuu reef), showed no significant difference for communities composition between the initial period and end of the sampling period. Furthermore, The genetic diversity and population genetic structures of Drupella cornus populations from six localities in the northern Gulf of Eilat (GOE) and five localities in Tanzania (269 individuals) were investigated using mitochondrial cytochrome c oxidase subunit I (CO1) gene sequences. Overall, 108 haplotypes, 47 in GOE and 61 in Tanzania were revealed, with similar calculated haplotype diversity for all D. cornus populations within each location (0.9 +/- 0.00025 and 0.903 +/- 0.00078. respectively). Only one haplotype was shared between the GOE and Tanzanian populations. Network analysis for the 108 COI haplotypes displayed two major clades, separated by nine mutations. Bayesian analyses of population structures revealed two clusters highly correlated with the collecting region. Analysis of molecular variance showed 73% of the molecular variance for all Drupella populations is a result of the differences among regions. Within regions, most of the molecular variance is based on within population differences, 89% north vs. south in Tanzania and 98%, Israel vs. Jordan in GOE. Fu’s and Tajima’s D values for all populations were negative, suggesting that the Drupella populations in GOE and Tanzania underwent population expansion or purifying selection. Conclusively, with the cost for establishing the nursery standing at 0.1 USS per fragment and that of transplantation at USS 0.19 per colony, the results indicated that large quantities of coral colonies can be generated and transplanted in damaged reefs at relatively low cost. Cumulatively, field results and economic evaluations showed that transplantation of nursery-grown colonies might uphold critical ecosystem functions, while successfully used in reversing coral reefs’ phase shifts states. Furthermore, a study on population genetic of D. cornus demonstrates that the distance between the two regions, GOE and Tanzania, provides for the observed differences in genetic structuring. Furthermore, the existing oceanic dispersal patterns governs the observed within regions population genetics variations.between Tl and T2 a result which is in contrast to the among species comparisons in Tl, at each site. A within treatment one-way ANOSIM comparison for fish assemblages performed between the first and last three months of the transplantation year (Kitutia reef) revealed strong separation (Tl, Global R = 0.743, P <0.001; T2, R = 0.445, P < 0.001 and T3, R = 0.694, P < 0.001) while the same treatment revealed weak separation at Changuu site Tl (R = 0.035, P >0.262) and T2 plots (R = 0.1 19, P < 0.043). Similarly, one-way ANOSIM done on the initial and last 3-month periods on invertebrates' community composition (at all sites, except Tl of Changuu reef), showed no significant difference for communities composition between the initial period and end of the sampling period. Furthermore, The genetic diversity and population genetic structures of Drupella cornus populations from six localities in the northern Gulf of Eilat (GOE) and five localities in Tanzania (269 individuals) were investigated using mitochondrial cytochrome c oxidase subunit I (CO1) gene sequences. Overall, 108 haplotypes, 47 in GOE and 61 in Tanzania were revealed, with similar calculated haplotype diversity for all D. cornus populations within each location (0.9 +/- 0.00025 and 0.903 +/- 0.00078, respectively). Only one haplotype was shared between the GOE and Tanzanian populations. Network analysis for the 108 COI haplotypes displayed two major clades, separated by nine mutations. Bayesian analyses of population structures revealed two clusters highly correlated with the collecting region. Analysis of molecular variance showed 73% of the molecular variance for all Drupella populations is a result of the differences among regions. Within regions, most of the molecular variance is based on within population differences, 89% north vs. south in Tanzania and 98%, Israel vs. Jordan in GOE. Fu’s and Tajima’s D values for all populations were negative, suggesting that the Drupella populations in GOE and Tanzania underwent population expansion or purifying selection. Conclusively, with the cost for establishing the nursery standing at 0.1 USS per fragment and that of transplantation at USS 0.19 per colony, the results indicated that large quantities of coral colonies can be generated and transplanted in damaged reefs at relatively low cost. Cumulatively, field results and economic evaluations showed that transplantation of nursery-grown colonies might uphold critical ecosystem functions, while successfully used in reversing coral reefs’ phase shifts states. Furthermore, a study on population genetic of D. cornus demonstrates that the distance between the two regions, GOE and Tanzania, provides for the observed differences in genetic structuring. Furthermore, the existing oceanic dispersal patterns governs the observed within regions population genetics variations.