Hey glad the urchin is working out, im thinking my sand may be the cause of some of my similar problem, may take it out and wash and add less. its looking black/grey in a few isolated areas. BTW, That urchin isnt a Tuxedo I got the same one heres a link to what its called, theres a common name but i cant remember it.
LMK if your problem returns or if just getting rid of it was the answer.
Brent
http://www.liveaquaria.com/product/p...594&pcatid=594