You can absolutely use dechlorinated tap water. Many saltwater hobbyists do this for FOWLR tanks and see no health or appearance issues resulting.
If, however, you are entertaining the notion of getting in corals or if you find that despite carefully planning and stocking you have algae related issues, you may wish to consider ROdI or just dI water.
Since somebody out there is rather enamored with the thumbs down button for my recent posts, CP Brightwell has the following to say about reverse osmosis filtration in his book, MARINE CHEMISTRY.
-----"Reverse osmosis (RO), also known as hyper filtration (HF), is the process of forcing source water through a semi-permeable membrane (essentially, a tightly wound sheet of material with very tiny perforations), removing dissolved and particulate substances that are physically larger than the diameter of the pours and/or are electrochemically rejected by the membrance material."
He goes on to describe the benefits of particular interest to reef hobbyists including the removal of silica and, when used in conjunction with pre-filter cartridges, large particulate substances (such as oxidized metals), pesticides, dissolved organic material, and chlorine.
Anywho, what this means for reef keepers is that, when well maintained with membranes that are changed on appropriate basis when the TDS (total dissolved solids) creep up in the output water, greatly cuts back on both the things that feed nuisance algaes and compounds that are detrimental to coral health.