I have a long spined urchin
Last night I was watching him shift over the glass and all of a sudden he started to squirt out tons of white stuff from about four or five places on his upper shell around the top. It came out in ribbons but soon dissapated into the watercolumn, making it very cloudy indeed. Have seen him expel detritus from his anus(?) before and it definately wasn't this. He seems to be perfectly fine after the experience.
Can anyone shed a light on what this was?