Grasshopper filters are engineered to filter down to 5 micron, so any particle larger than 5 millionths of an inch is trapped. As long as you change the filter as recommended, the chance of "wet sanding" all the parts is slim. Anything below the 5 micron will polish the parts. Drives take a lot of abuse, and they will have issues. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.