This study aims to inventory the type of necton, knowing the structure of the necton community and measuring the critical thinking skills of students of class VII.1 SMPN 1 Ujan Mas Kepahiang. The results showed that the necton obtained from the Taman Pintar pond amounted to 7 species and Pipi Putih Pond totaling 4 species. The necton species in the Taman Pintar pond  with the highest KP, KS, and FK values are tin head fish with KP, KR, and FK values respectively  0.102 idv / m2, 75.71% and 83%. While on the Pipi Putih Pond is local catfish species with the value of KP, KR, FK of 0.01 idv / m2, 39.29% and 25%. Then dominance index (H ') in the Taman Pintar pond is 0.61 and C' Pipi Putih pond  = 0.76. While the index of diversity of necton species in both ponds also belonged to very low category with H’ value of Taman Pintar Pond = 0.28 and H' of Pipi Putih pond  = 0.17. The result of Percentage Of Agreement test showed that  environment-based learning tools developed are included in the category highly feasible to be tested. Students’ critical thinking ability on the perpormance aspect shows 33 ,3 % percentage including critically critical criteria and 66,7 % including critical criteria. While Students’ critical thinking ability on the cognitive aspect shows four criteria, that are very critical as 26 %, crittical criteria 40 %, criteria critical enough 27 % and  criteria less 7 %
                        
                        
                        
                        
                            
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