Phylum Bryozoa
Bryosoans are very small. They are sessile but can live on moving things. They are are filter feeders. They filter feed by turning the tentacle sheath inside out to expose the tentacles to feed on bacteria. Bryozoans come in an array of colors.
Note: the anatomy found here was better at explaining the way the zooid retracts and then feeds than the text. Although reproduction is not discussed in any of this. So far no one has noticed. They are not as “into it” as other projects have distracted them.
The Inclusive Atrium 