I've often thought about this, as it would be handy for me (tank is upstairs not near a water source) to have a bottle of water for top ups from evaporation. But then I thought about the mineral content if that would harm them, and I also thought about the leechates out of the plastics - they say not to drink bottled water if it's been somewhere really warm or in sunlight, or if the bottle is old (it has a best before date on the bottle, not because water goes off but because the plastic bottle releases stuff into the water)... so I don't know
forgive my lack of scientific jargon as to what comes out of the plastics... I got up late and had to rush to work and I'm here half asleep