09-16-2006, 05:52 PM
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Doesn't look like coral, but I'm not sure. But it could contain some kind of calcium carbonate. An easy way to tell is if adjust your pH is to test your water from your faucet tap. If it's lower than your tank, then something in your tank is causing high pH, which could be the rock. So then, basically remove the rock, replace all of the water and check your pH again.