Hi,
My friend and I have used city of savannah water that have been filtered through RO Filter and used it for our reef tanks for 3 years. we had great results. currently we have a 300g system with alot of coral and live rock. so please contact me if u need any help. also you can measure your tds reading of your water after running through you ro. and make sure to replace your RO or DI when it needs it.
Thank you and good luck.