TJ from http://www.aquariumtiptank.com goes through how he uses his Mikro Series Omega Portable RO/DI Water Filtration System to filter his tap water and achieve 0 TDS water for his saltwater aquarium.

At Aquarium Tip Tank, we recommend that you use an RO/DI filter for all of your aquarium water no matter what type of fish tank you keep. It is essential for a saltwater reef tank, and can only help keep the water quality of a freshwater fish tank clean and the water parameters steady.