Dish soap can be used in an ultrasonic cleaner, but you need to be careful about its compatibility with the material you are cleaning. For example, using water and dish soap with some metals can cause rust and corrosion. In this case, it is a far better idea to use a special ultrasonic soap that contains rust inhibitors, for example, Brulin 815GD. In general, using a detergent that is specially designed for use in an ultrasonic bath is the best option.