An easy way to look for small external parasites is doing a skin scrape. If you are careful, you can use a microscope coverslip, or if not, a razor blade or scalpel. Start behind the operculum and apply gentle pressure as you move posteriorly. Apply the coverslip to a slide and look at it under the microscope. Scan at low power first, and then at higher magnifications.

With practice, a small skin scrape may carefully be performed on live, unanesthetized fish. Refer to the section of FishGuts called "Sample Cases" to view actual skin scrapes through the microscope.