Safety concerns. Always marinate meat and fish in the refrigerator. You can use some of the marinade for basting after removing the meat or fish from it only if you bring the marinade to a boil and cook for five minutes to kill any bacteria.
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.
The main reason for running the pool pump during the daylight hours is to ensure proper sanitation. Chlorine is degraded by sunlight, so there is a larger demand on the chlorine residual during the day. When the pool pump is operating, the circulation in the pool disperses the chlorine throughout the pool. Also, most pools use some type of chlorinator that adds chlorine only when the pump is running. By running the pump during the day, it helps keep the chlorine at a constant level. Use of the pool also consumes the chlorine, and most swim during the day. Having the proper levels of chlorine helps kill algae spores, germs, bacteria and other contaminants as soon as they enter the pool.