Sometimes called a thermal blanket or bubble cover, this cover floats on the surface, magnifying the sun's rays to warm the water and also provide chemical/heat/water evaporation. There are various options available such as the Blue, Silver and Gold. And come in various thicknesses. To purchase a solar cover click here.

A solar cover is a tarp that covers your pool.

a must for using any other type of heater because they help heat the pool by day and prevent heat loss by night