"The often-used blanket statement that "reverse osmosis does not remove chloramines" is technically true but realistically false. While the reverse osmosis membrane itself does not remove chloramines, every respectable RO unit is equipped with two or more high quality carbon filters. Pre-filters, the filters that process the water before the membrane, receive water at a very slow rate of flow and therefore work under excellent conditions for chloramine reduction. The use of the high quality cartridges described by Mr. Bauman actually should provide superb chloramine reduction in an undersink RO unit, yet the "reverse osmosis does not remove chloramines" myth continues to be promoted by sellers of non-RO products."
I use RO/DI for my reef tank and have never added any sort of dechlorinator during water changes and my livestock (variety of corals) are perfectly fine. I should also add that I use the standard carbon blocks instead or the recommended catalytic carbon. Honestly, I don't know if anyone in the reef community bothers with dechlorinators when using RO water for mixing saltwater or for topping off, but I doubt many do.