Some varieties of water fleas are planktonic, but others live on the bottoms of lakes or attached to aquatic plants. Extremely prolific, thousands of the small animals may inhabit a single square meter of water and are, therefore, an important part of the food chain. Most water fleas feed upon phytoplankton or decaying organic material, but some are predaceous and may feed on smaller members of their own order. In turn, water fleas are a fundamental diet component of a variety of fish, insect larvae, and other aquatic organisms.