Is a decomposer a predator or a prey? Explain

Decomposers are prey.

Explanation:

Decomposers break down (hence, 'decompose') dead organisms, and are heterotrophs, but are not predators. They do not actively go hunting, nor consume food like a predator typically would, and are not technically scavengers.

However, they are eaten. We eat mushrooms and fungi all the time. Other animals eat them. This constitutes them as prey.