In the freshwater food web,

the relationship between the minnow and the water fleas can be described as ...

In the freshwater food web,

the relationship between the minnow and the water fleas can be described as Predator-prey relationship

Explanation:

A food web can be described as a diagram which shows multiple food chains. It represents the 'predator-prey' relationship in an ecosystem.

The freshwater food web will described all the predator-prey relationships in the fresh water.

The minnows in the fresh water feed on larval fishes, mosquito larvae and water fleas. Hence, minnows will be the predators and water fleas will be the preys. So, these organisms will show a predator-prey relationship.