PDX_Reefer Posted April 17, 2016 Share Posted April 17, 2016 I have a IM 20gal QT tank that currently holds no fish, just some live rock, a few corals, snails and hermit crabs. Came back from a short getaway to find a large area of one rock covered with a white substance. It looks to be accumulating on the CUC shells as well. Chemistry is all good. 1300Mg, 400 Ca, 8.1 KH. Nutrients low, pH and salinity good. Lights were running about 8 hours daily. I dialed that back to 6. Doesn't appear to be easily scraped off. Any ideas what it is? Thanks. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
TheClark Posted April 18, 2016 Share Posted April 18, 2016 Head scratcher! Do you have urchins? They can turn live rock white again by scraping.... 1 Quote Link to comment Share on other sites More sharing options...
PDX_Reefer Posted April 18, 2016 Author Share Posted April 18, 2016 No sea urchins. Just a few hermit crabs and a few snails. Hasn't advanced or spread to the other rocks since I first noticed it but it isn't receding either. Whatever it is, it appears to be accumulating on the crab and snail shells. I did cut back some of the palythoa polyps near the white area to reveal the zoa polyps and let them get some light. Wondering if the released palythoa toxins could have done that. Rock looked fine for about a week or so after the trim so not sure it's related but it's the only thing I can think of that's different about that one area that's now white. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
matty Posted April 18, 2016 Share Posted April 18, 2016 Is a layer stripped off or is the white a layer on top of the rock? If it's on the rock, is it hard or soft to the touch? Quote Link to comment Share on other sites More sharing options...
milesmiles902 Posted April 18, 2016 Share Posted April 18, 2016 Looks like precipitation to me or maybe coralline? Quote Link to comment Share on other sites More sharing options...
PDX_Reefer Posted April 18, 2016 Author Share Posted April 18, 2016 It looks/feels like a layer on top of the rock. Hard to the touch. I tried to scrape away at it with a fingernail - no go. I haven't yet tried anything more forceful. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
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