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?
