Swimming pool filters are an important part of maintaining a clear swimming pool. D.E. filters filter the finest partials, but can require regular maintenance. Cartridge filters are in between D.E. and sand when it comes to filtration and maintenance. Sand filter require the least amount of maintenance but don't filter as fine of particles, there are other filter media types you can add to a sand filter to improve filtration.
There are several options for heating your pool. Gas heaters have been the main goto option and are the work horse of heaters. Heat pump are a more efficient than gas heaters and are available in heat/cool units. Solar heaters are another option and are the most energy efficient of all heaters.
Pumps are the heart of your swimming pool. Variable speed pumps will save money on energy costs, and you can upgrade your existing pump to variable speed technology.