Rainwater in fish tank

[LaBelleDameSansPatience]

I have used rain water for years for our aquarium. Now I read that I should not have done that, but that one can't change to tap water due to the different pH. Fish always seemed quite OK and enjoyed the daphnia/mosquito larvae which are often in the water butts.
100 L tank, one fish shaped goldfish and one fancy goldfish. Both inherited and I know that the tank is too small, so will be looking to rehome 'normal' fish ….
Should I change from rainwater to tap water? If so, how?

If it works for you it works. Some people advise against rainwater because of air pollution or contamination from roof tops. If you want to change to tapwater it is easy to do so. Remember to use dechlorinator in any new water you put in and only change 25-30% of the tank volume at each water change . The fish will acclimatise gradually this way to the different hardness and pH of the tapwater.

Thank you … not too much air pollution where we live and I test the pH in the aquarium. To my surprise it is 8 … presumably because of the gravel in the tank. Might be easier in the winter to use warm tap water rather than heating buckets of water butt water to the right temperature, so might carefully change ...