I'd beware of the ultra cheap 'ultrasonic' cleaners. I was in a store a while back and asked for an ultrasonic cleaner; the clerk pulled out a box, only 20 dollars, which said 'sonic jewelry cleaner'. For 20 bucks, how could I go wrong? Took it home and used it, and discovered all the thing did was vibrate and rattle around. I saw right away that this was not an 'ultrasonic' cleaner. A true ultrasonic cleaner cannot be had for such a ridiculously low price; decent ones can be had for around a hundred dollars, but I have never found them for much less. Even with a good one, be careful since the tiny bubbles created can get quite powerful on some objects such as your glass wicks and the coils. I think they typically operate somewhere in the 40+ khz frequency range; they do not simply sit and shake things around.