Yes! Heaters can be added to your natural pool in order to keep it readily available throughout the winter months. Make sure that you monitor exactly how warm its getting, and that your plants will be able to handle the temperature increase. You may want to use a cover to preserve heat while the pool isn't being used -- just make sure not to cover the regeneration zone.
Other ways to keep your pool warm include coverage at night, as well as placing your pool in the part of your yard that gets the most sunlight during the day.
