Now is probably not the most needed time to learn about pool heating but here we go anyway. In order to keep a pool warm, your pants warm from all the extra money in your pocket you should do the following for your pool.
1.) Buy a thicker more reliable pool cover.
2.)Install a solar powered or high efficent heater.
3.) Operate the pump less or buy a more energy efficent one.
4.) Lower water temperature or turn off equipment when you are going on a trip.
5.) Deal with the cold
6.) Move to Arizona, Mexico or any other really hot place.