Hi, the question was intended for Crystal.
Rainwater is mostly fine, when you filter out the pieces of leaves and stuff that regularly comes with it.
Sometimes in dense areas i would be carefull using it after a period of dright,
i believe it also takes all kind of floating pieces with it that are out in the air,
like exhausting gasses.
I was talking about purified water.
Like in osmose or distilled water.
This will cause a reverse osmose effect between water inside you're frog and the water he sits in.
I posted it somewhere on a topic that is about the differences in water.