Fellow enthusiast Rushton has published in Positive Feedback, here on the Analog Forum, and again on Vinyl Asylum, that he is using a home-made ultrasonic cleaner and his bath contains isopropanol and a nonionic detergent, diluted in distilled, deionized water. If you want his opinion and experiences, you may want to find his threads or his article. Without having done it, my personal opinion would be that adding at least a low concentration of nonionic detergent should be advantageous, because it reduces the surface tension of water, thereby allowing it to penetrate further into the grooves, and the detergent effect also should help in solubilizing crud. (I am not sure why you want to restrict responses to those using Klaudio, but I do apologize if you find Rushton's work to be irrelevant on that basis. I found it interesting, because in almost all other cases, including yours, ultrasonic cleaning is done with "pure" water, if not holy.)
