How do you clean your refractometer? My usual procedure to clean up before putting away is to wipe the SW off both the cover and prism. Then with a paper towel, dip some RO/DI water and wipe the cover and prism off. Lastly, one more wipe with dry towel. What else should I be doing/not doing? Also, if you are testing several tanks, do you clean between tests? At this point I just wipe off the cover and prism but don't clean it with RO/DI.