Urchin?

[stevenc23]

Tank has been up and running about 4 months. Started with dry rock and sand but topped sand with 20 pounds of Tampa Bay Live sand 3 months ago. Cleaning my tank today saw a "clump of sand" crawling along the bottom. I have added some snails so figured it was a dirty snail. Here is the best pic I could get. Only thing I can think of is that it came in the TBS sand. Purple sea urchin?

 

[UncommonSense]

Definitely an urchin! Likely a purple urchin…

I had one come into my tank as a spiky pancake-shaped juvenile on a single live rock, a red slate pencil urchin… it’s around 3” diameter by now!