Many people run it at night, however it is highly ineffective and ends up costing more in both time and money.
The daylight hours are when the sun is hitting your pool and your pool gets used the most, that is when you need chlorine filtrating through your system. Algae needs four things to form and survive. The Sun is one of them, and you are giving it free access if you run it at night.
It may be cheaper to run the pump at night, but honestly you should run it 1 hour a day per 10 degrees of temperature at least, and it should be during the day. Running the pump at night should only be when you are doing a major chemical treatment such as algae clean-up. Your pool is more vulnerable during the day, plants don’t grow at night the way they do during the day–that’s true of ALL plants including Algae.