DIY Remedy - Minimize mark that a blemish may leave by mixing 1/2 teaspoon baking soda and 1/2 teaspoon distilled water to create a paste. Apply to affected area for 5 minutes;splash off. After, use cotton swab to dab on hydrogen peroxide. Prevents darkening. Worth a try!
DIY to heat pool. made from black plastic tarp (polyethylene film) that's been soldered to hula hoops. They float on the surface of the water and attract heat from the sun, thus heating the water in the pool in the process.