They can also play an important part in keeping the water in which they live clean. For example, biologist T. M. Frost found that, at its peak density, the sponge population in one New Hampshire pond could filter the entire volume of the pond in about a week. During active summer growth sponges can also reproduce sexually. The fertilized eggs develop into free-swimming larvae which settle and metamorphose into new genetic individuals. Like sponges, freshwater bryozoans have few species, but they may be very common and play an important role in freshwater ecosystems.
Bryozoans use ciliated tentacles to filter suspended particles as in the photo at left.
Colonies may form tan branching networks or brown fuzzy masses on rocks or pond weeds. One species, Pectinatella magnifica , can be really noticeable. Statoblasts are asexually-produced dormant buds with thick protective shells. Their structure and shape are unique for each phylactolaemate species. Biologists think that asexual reproduction is the fastest and energetically cheapest way for an organism to make new members of its kind, members that are proven to be adapted to the same environment as the successful parent.