Aquarium fish SPA still the popular procedure. But if you will be lucky enough to meet that tiny fishes in real nature, they can clean your Rudraksha-mala in a most divine way. You can download this video of washing the Rudraksha-mala with fishes.
Its easy to fins that fish in a cold rivers from watertfalls, starting in a national parks of the country (this video made in Thailand, Phangan island).
Remember to visit my Rudraksha dedicated multi lingual website to check the news there.