You should first check your source (tap) water for hardness (GH) and alkalinity (KH) and maybe pH. Check your water samples right after dispensing from tap and then again after a 24 hour off gassing period. Write those numbers down so you can compare if they are different.
You may or may not need to add cichlid salts and/or buffer depending on a few factors such as your water test results, whether buying wild caught cichlids, which species cichlids you plan on keeping and how your local fish shop keeps their fish water parameters.
Sorry I did miss that you were planning on using RO water so you will need to buffer the aquarium water so hopefully someone with more experience will comment for you. What is the reason you plan to use RO water?