No, the fan is always on (if it wasn't, the GPU would overheat in a few seconds). Most overclockers set a custom fan profile. Use the program MSI afterburner and make your fan speed go incrementally up. Personally, I have mine set to go steadily up and once the GPU hits 70 C I set my fan speed to about 68%. At 60 C I have my fan speed set to about 50%. The best way to find out what fan profile works best is to test it yourself through overclocking and checking your temps while stress testing your gpu because it differs based on your card and your overclock.
Also, the cooler master h100i is not actually cooling your GPU, only your CPU. Your GPU most likely has 1-3 fans of its own cooling it.