Generally you can coax some fecal material out and place on a slide. If high in liquid no additional fluid is needed though adding some helps to flatten things out with a cover slip. If protozoans are present you'll see a lot of zig zag random movement and they'll run in directions divergent from the ebb and flow of the solution. Many reptiles can carry them asymptomatically so treatment may not neccesarily be required unless the population is so dense as to cause regurgitation. As the last writer alluded to Flagyl (a brand name for metronidazole)is the drug of choice but don't rush in to fix a "problem" that isn't affecting the reptile to some discernable degree. A vet can supply liquid flagyl or you can generally find it in tablet form in fish medication displays at pet stores. A sugar syrup including metronidazole is sold over the counter in Mexico (Tastes nasty!)and other countries. It is generally used in those cases for diarhea caused by bad water or contaminated foodstuffs. It acts as a anaerobic antibiotic and is commonly used for such things as clamydia in humans. Human dosage is generally in the realm of 250mg three times a day for a week. Good hunting...