Recently, the folks in my area got enamored with the topic of “nano‐bubbles” for the reef tank. Being a curious engineer and avid tinkerer of tanks, I jumped right in to test it for myself.So what are nano‐bubbles and what is the concept being prescribed? Well, there are many sources online that talk about the benefits of nano‐bubbles in various applications, from water and food processing to cleaning applications such as wastewater treatment. But with respect to our hobby, one site, Elegant Corals LLC, had been promoting the benefits of running “micro‐scrubbing bubbles” in the reef tank for some time. You can check out their Facebook page for the claimed benefits. Process The basic process, in short, is to produce the smallest bubbles possible and inject them into the main tank via the return pump. Wooden airstones are placed just before the inlet of the sump return pump, and the amount of bubbles is controlled by adjusting the distance from the airstone to the inlet.