Zebra mussels also colonize soft, muddy bottoms. Hard objects, such as pieces of native mussel shells, act as a base for settling veligers. As a few mussels begin to grow, they serve as substrate for additional colonization. In this way, extensive mats of zebra mussels can form on soft lake and river bottoms. They strain water for the food they need.
Unused food is bound with mucous into a pellet called pseudofeces, which is ejected.
Each adult zebra mussel can filter about one liter of water per day. Nearly all particulate matter, including phytoplankton and some small forms of zooplankton, are removed. These microscopic plants and animals are the base of the food chain. Small fish, such as young sportfish or forage fish, depend on this food for survival and growth. The long-term consequences of removing so much food from the environment is still being studied.