Distilled water is made by boiling the water and then condensing the steam. Distilled water needs to be supplemented with proper minerals to be effective for frogs. It is important to know that distilled water can be too pure to support life! I have used regular tap water treated with a good water conditioner, like Stress-Coat, for many years with great success. If you feel that your tap water is out of tolerance, try bottled spring water. Bottled drinking water comes directly from the tap or reverse osmosis!