The Cyanobacteria strain of Nostoc originally from extreme and non-extreme temperature areas had been observed to obtain the growth curve of those strains which were incubated in 20°C with BBM medium. The strains which used were HS-5 strain isolated from Ciseeng, HS-20 strain isolated from Pancar Mountain and UI-29 strain isolated from Mahoni small lake in Universitas Indonesia. The water temperature of habitat ranges were 36 - 43°C (Ciseeng), 46 - 69°C (Pancar Mountain), and ±29°C (Mahoni small lake). Incubation temperature was 20°C, while the parameter was biomass wet weight during growth. Medium, which was used, was Bold Basal Medium (BBM). Observations were done in a period of 7 days. Each treatment was made in two replications. The result showed that all Nostoc strains experienced adaptation phase (lag phase). The growth curve of Nostoc HS-5 and HS-20 incubated at 20°C slightly increased, while the growth of Nostoc UI-29 strain incubated on 20°C was slightly decreased. The highest biomass weight of Nostoc HS-5 strain was 10.3 mg/mL, which occurred at sixth day (t6). The highest biomass weight of Nostoc HS-20 strain was 17.3 mg/mL, which occurred at the second day (t2). The highest biomass weight of Nostoc UI-29 strain was 22.3 mg/mL, which occurred at first day (t1). The highest growth rate between all strains is Nostoc HS-20 strain based on its average of biomass wet weight, so the conclusion is Nostoc HS-20 from extreme temperature area has an optimum growth in 20°C.