According to http://www.atlantawatershed.org">www.atlantawatershed.org</a>, you are correct. Thank you for the correction.
I'd also like to add, not everyone can just run out an buy and R/O unit. The guy has like 3 rocks in a 20 gallon tank(no offense intended, we all start somewhere) and is asking a water dechlorinator question. Even a cheap R/O is going to double the startup cost of the tank. We need more information on what he intends to do before we tell him to just buy the unit, hook up the unit, run the unit, don't get impatient and forget the unit is running, buy a mop, mop up the water, buy a float valve and trashcan.
As for selecting a unit, if that's what he's looking for, I'd go with a Kent Deion 200. Unlike R/O, there's no waste water, and no startup impure water. The first few gallons that come out of R/O after each start are impure, do the the loosening of particles, which makes topping off with one silly. Yes DI comes at a higher cost per gallon, but it's easier to run, maintain, and does 200gpd pure out of the box. And once he gets his feet wet with the unit, he can reorder bulk mixed bed resin and easily refill carts at an even lower cost.
So for a better answer, GOODOLEBOYZ250, what are you planning for this tank?