Research were conducted to observe the temperature tolerance of Stanieria HS-31B and HS-48 in a 20°C environment. Stanieria HS-31B was isolated from Maribaya hot springs with a habitat temperature of 42°C while Stanieria HS-48 was isolated from Ciater hot springs that have a temperature of 38°C. The strains were cultured and incubated in 20°C for 7 days. The growth parameters of Stanieria HS-31B and HS-48 were measured by counting the cell density and measuring biomass weight during the 7 days of observation. Cell density consists of two cells, the baeocyte and the vegetative cells. Vegetative cells develop into endospores, which are then released as baeocyte. Biomass weight was calculated by subtracting the weight of the tube from the weight of the tube and pellet. The results from calculating cell density and biomass weight showed that Stanieria HS-31B and HS-48 can grow in 20°C. The highest and fastest cell density was observed from Stanieria HS-48 with 1.08 × 106 cell/mL of baeocyte and 0.10 × 106 cell/mL of vegetative cells. The highest biomass was observed from Stanieria HS-48 with 0.003 mg/mL. Strain of Stanieria HS-31B and HS-48 are probably the mesophilic cyanobacteria.