Ribbon Worms - Nemertea

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Saw one of these about five years ago in my tank and have not seen it since. Figured it just died. Happen to look in the right place at the right time and saw what appeared to be the same worm. Only have a picture in the book Coral Reef Animals of the Indo-Pacific.

Nemertea- Ribbon Worms. This one is the Notospermus tricuspidatus. Black with green and white zig zags on the flattened head. Probabley about 4-5" long.

Any thing I should know about this?