+1 Fish. I have 2 long spine black urchins in 2 different tanks, if the spines are breaking off that would be normal of an unchin growing and breaking off as it spines outgrow its environment. But completely loosing spines for an urchin is a sign that its health is going down hill and its water params are not right. I have had a long spine in my 60g tank for a year now and he has broken off (NOT LOST) his spines many times as his body has grown. If your urchin is LOOSING spines test your water something is wrong,