yup. so you mention fresh water could kill your live rock, now you probobly mean like if you put live rock in 100% freshwater. The reason i asked the question is because the live rock i have in my tank looked good in my oppinion. It had a brown sorta color, some algae and i have a piece or 2 now that have completly changed there look. I topped off my tank one afternoon with freshwater, i added maybe a gallon of water to my tank, the water i added was declorinated and it sat for an hour or so before i topped off the tank. The next morning is when i noticed the change in my rock its sort of a green crusty color, its not pertuding from the rock its not long or wavy its like the rock color changed. I was curious what it was so i tried to scrape some of it off and its very tough, so im pretty sure its growth of some sort. Im sure my description doesnt mean much with out a picture but now ive told you the hole story, maybe you can make sence of it. ill try to get a pick of my rock.
thanks for responding to the thread