I have one gold and one black mystery snail. the gold has become almost 3 times the size of the black due to his undying hunger. He eats prettymuch anything he can get into his mouth and chew. Anyway, on occasion, the black snail will climb atop the yellow snail and he will be near the edge of the shell but I can't ever tell if he's biting the golden or if he's just hitching a ride. Obviously the golden snail doesn't like this because he will get into position and rock himself back and forth slamming the black snail against the glass or rock trying to dislodge him. Is this normal? I'm not to worried about it because they've done this off and on for a year now and no damage has ever been done but it is very comical. Just wondering what the deal was. Kyle