The R.O. Water debate

Wasn't sure whether to go for tap water (which contains 0.1mm of nitrites - due to city water no doubt) or Reverse Osmosis water. Turns out i can use the tap water as long as i leave it out for 24hrs, use a water conditioner that gets rid of the nitrites, and perhaps salt it. Phew! having to carry all those bags of water from the car to the flat was not going to be pretty! If i go with RO, i will have to add minerals to the RO water as it has no minerals in it that the fish actually need! So, RO is great for drinking but not great for fishies, while tap water is good for fishies but not good for drinking .