yea its the black spot its nothing its carrying the spines around that area are missing, is it common for them to lose their spines theres nothing in the tank that would attack him
I honestly dont know. I have never kept them, just know what I have read as I try to become more knowledgeable with saltwater. Have you tried brushing up on the articles in Wet web media? They typically have a ton of good information and pictures when it comes to diagnosing issues.