If it does not move, I would say it is a foraminiferan. There is a pink version called Homotrema, but invertebrate zoologist Dr. Ron Shimek describes this in an article on forams (google foraminiferans Ronald Shimek
There are similar white foraminiferan species found in aquaria. Their bodies look like small "spiky" versions of a stony coral, rather like nano-sized versions of bird's nest coral, Seriatopora hystrix. These foraminiferans have not been identified to species.