Regarding watering, filtered water or softened water may essentially cause the plants to die from dehydration. Salt (sodium) will build up over time and may gradually cause degradation in the soil quality. Some species are more affected than others.
For this reason, we always recommend using tap water. However, tap water sometimes (depending on the region) causes limescale in the water tank, which in turn may clog the water transmitting wicks. Cleaning the water tank and wicks in a warm vinegar solution helps to remove limescale when necessary.