Bryozoan colony

Bryozoans are an invertebrate that live in colonies, similar to corrals. The following is an excerpt from a response from doctor Timothy Wood-
"They help keep the water clear. Many people write to me asking how to get rid of them, as though they were somehow dangerous. Of course they are not.
Although the species is native to eastern North America, it has now spread westward across the continent, jumped the Pacific to northern Asia, and is also spreading very rapidly through western Europe.
There are a lot of interesting things about Pectinatella and a lot we still do not understand. I hope you can hold onto your pond population for many years."