Yes chara is often a habitat for PK shrimp. Whether they hang out there because it is good protection, or maybe they eat little critters that make the chara their home I don't know. I do think the crunchy calcium nature of the chara helps but I also have read that PK shrimp love diatoms. I know you can order a diatom culture from pond management companies (or perhaps Carolina supply?). Also I have seen posts from azteca or Bill Cody where they can give you a recipe to make your own diatom stew.

send pictures?