Reactors aren't going to pull out the stuff that we are aiming to keep out by running Ro
units. Most of the stuff in the tap water, you along with most everyday people will have no means whatsoever to test the levels of. You could call the water department and ask them to share their test results and once you see the kinda stuff that is in the water you'll definitely not want to use it for your precious SW
tank. Especially since a lot of water sources can be contaminated by pesticides and other chemicals in a lot of areas.