Iron is a metal that not only is hard to completely remove from water, but also has nasty side effects - rust particles in the water, red staining on your sinks/toilets/showers and sulfur smell. A dual canister system with a sediment filter and a carbon filter can improve the water by taking out the rust particles and smell, but it won't remove totally dissolved iron.
Sediment filter Clogged with Rust particles Red Stains from Iron
The dissolved iron becomes part of the water solution, and passes through even the smallest openings in the filters. The dissolved iron also is what causes red staining and sulfur smell can be caused by iron-eating bacteria that give off hydrogen sulfide when they die.
So, how to remove the dissolved iron? We have had great success with the Metal Trap filter that is in our Essential System Plus Iron and Jumbo Essential Plus iron. The resin in the Metal Trap absorbs the dissolved iron from the water and removes the red staining. It also absorbs hydrogen sulfide to remove latent sulfur smell that gets through the carbon filter.