@laneyk @km6 said they have a Weddell shower filter. From what I can see, these filters use activated carbon as a primary filtration material and they can harbor MAC germs that can grow in the carbon material. So you would want to make sure that any shower filter you get does not use activated carbon. You also would need it to filter particles down to 0.2 microns. Then it will filter the MAC bacteria. I understand that Pall and Safe Water are two companies that make such filters.