I have my own 6 stage rodi unit I have purchased about a year ago since its a 45 minute drive (no traffic) to the nearest fish store. All of their canisters were brown and none of the employees could tell you when the last filter change was done. Before that I used water out of the sink with the water purifier drips you can buy. I have noticed no change to my corals with rodi water or adding the water drops. I still use the unit since I paid for it but when it comes time to buy replacement filters I might just go back to adding the drops to the water and sell the rodi unit.
I think it really has to do with where you live.
I think it really has to do with where you live.