Which of the following is NOT a common parasite found when performing a fecal flotation on a small animal?

The most accurate choice in this scenario is heartworm, as it is not typically detected through a fecal flotation test. Fecal flotation is primarily used for identifying parasitic organisms that reside in the gastrointestinal tract. Common parasites found via this method include tapeworms, roundworms, and coccidia, as they all produce eggs or oocysts that can be isolated and observed in fecal samples.

In contrast, heartworms, which are a type of nematode, reside in the heart and pulmonary arteries of dogs and cats, not in the intestines. Detection of heartworms usually involves blood tests that identify the presence of adult female heartworms or their microfilariae in circulation, rather than a fecal examination. This distinction makes heartworm the irrelevant option when discussing parasites identifiable through fecal flotation tests.