Hi, I have used rainwater in my tank for over 3 years now, with almost no tap water ever going in. However, of course now the GH and KH are almost non-existent and I would like to raise it a little. This can easily be achieved with the local tapwater! As the rainwater is stored in 25l jerry cans for a couple of days to warm-up before going into the tank at each water change, presumably I could just add about 10% tap water to the cans and leave as it warms up? Presumably this way, the chlorine will have left the tap water, and there's no need to add water preparation chemicals into the water?