Protozoan communities are ecologically fascinating systems that provide a magnificent opportunity to investigators interested in testing various ecological hypotheses. In many instances, these communities fit models developed for higher organisms. The small size of protozoan communities and the speed with which events occur are simultaneously advantageous and frustrating. In a small space and a short time, research can be accomplished that would take many years for larger organisms. However, rapid movement of individuals and turnover of species make individual interactions difficult or impossible to detect and quantify, unless the components are studied in isolation from the remainder of the community.