I bought a smallish ultrasound tank cleaner device for not much money, battery powered, but it appears to be too wimpy for any real life job. I dosed my eyeglasses in it to try to remove soap spots, zero success. My brother in another US state, does have a larger one, looks like the real thing, that i will try next summer. Meanwhile if anyone has tip on how to remove soap spots from eyeglasses lenses, i would appreciate hearing. Also a real working ultrasound tank i think would be just the thing for cleaning up old grungy air - variable caps.