Hi folks- just learned how to post and attach a pic (I'm a little slow with this stuff). This brown stuff has been around for a couple months. At least that's when I noticed it. It doesn't seem to get bigger or smaller. It's almost like the rock is stained. I just added a third kissel 150 over the area and I'm not sure if it will take off. I haven't noticed any anywhere else. Parameters are all good: calc-450, nitrates 5-8 range, phosphates .03, alk 10. I have a 40 gal w/skimmer. Good flow. No diatoms and little algae. I think my tuxedo urchin may have died after eating some. Thanks in advance for any help. I have also considered taking the rock out and nuking it but I'm not sure what to use.