I recently purchased two amano shrimp for a 20gal fish-only tank, and I just noticed the first molt on the substrate. Should I get it out of there now to minimize nitrate, or should I leave it to let the shrimp eat?
Definitely leave it there. Even if the shrimp that molted doesn't eat it, the other shrimp will likely do so! As Feohw said, they gain some calcium from eating it, which in turns is good for a strong, healthy shell.