The amount of hose you use is entirely up to you. Fifty feet is sufficient in most cases. Keep in mind that the longer the water is in the hose, the warmer it will be when it exits. A longer hose may allow you to increase the volume of water traveling through the hose and warm the pool more quickly.
NO! Any dark colored hose will work. Of course the darker the hose the better it will capture the solar heat from the sun.
This is a difficult question to answer because there are so many variables. The very first requirement is SUN. Hose color, length and positioning are other variables that play a huge role in the amount of heat you achieve. For example, a dark hose on cement will produce better results than a green hose on grass. Another major factor is the volume of water traveling through the hose. If the volume of water is too large, the water will move through the hose too quickly and not be heated. We recommend a stream of roughly ½-inch diameter to produce a good temperature.
When used properly, this Device has little if any effect on pump operation. At no time should the Device totally obstruct the flow of water to the pool; even in the closed position water is directed to the hose outlet. Compared to the stress a pool vacuum places on a pump, you shouldn’t notice any difference in your pool operation.