Originally Posted by mr_X
again, it's the mouth you are viewing. just leave it be and make sure your parameters are perfect and it should return to it's beautiful state in no time. if it doesn't, it's because your water is not right.
splitting is generally due to stress. it could be splitting, but that's sort of how an anemone poops. it deflates and opens it's mouth and expels a brown substance. if the mouth keeps getting wider and wider instead of bouncing back in a day or so, it might very well be splitting.
if it's not pooping, but splitting, i would make it a point to find out what it's not happy about.