I think below 20 degrees it can get skin problem so try to arrange some battery and ups or if u can arrange 12v heater if possible. As if temp go below 20 and remain for more time then problem will come, I think koi can live but glow no. U can check more on net also and be prepare for winter. Best of luck
Bhai glo tetra hardy fish hai kya
Hamare yaha winters bhout hoti hai aur light ki samayasa hai to kya ye bina heater bhi survive kar sakti hai kya
I think below 20 degrees it can get skin problem so try to arrange some battery and ups or if u can arrange 12v heater if possible. As if temp go below 20 and remain for more time then problem will come, I think koi can live but glow no. U can check more on net also and be prepare for winter. Best of luck