Background Paragraph: Protozoa generally feed by engulfing and digesting other organisms. As consumers, they have various roles in food chains and webs. Some are predators. They prey upon other single-celled organisms, such as bacteria. In fact, protozoa predators keep many bacterial populations under control. Other protozoa are herbivores. They graze on algae. Still others are decomposers. They consume dead organic matter. There are also parasitic protozoa that live in or on living hosts. For example, the protozoan that causes malaria lives inside a human host. Protozoa are also important food sources for many larger organisms, including insects and worms. 
Story: George is investigating some algae that has recently started growing in his pond. He wants to find something ti prevent it from overtaking the pond as it makes it very hard to see under the water. After a bit of research he finds a protozoa that can help him. 
Question: Given the protozoa can successfully reduce the algae in the pond, is it a herbivore or a carnivore?
herbivore.