It is reccomended by the fog machine manufactures to use distilled water in them or the minerals in regular tap water can shorten the life of the fogger. You should also use distilled water in your hand misting water bottles as that will help keep water spots off the glass. In the frog's water dish you can use regular dechlorinated tap water. There was a thread about the different water awhile back...try a search on it as John goes into more detail.