I have 2 fighting conchs in my tank and they don't bother anything too much even though they are large. I originally got one and then I didn't see it for weeks, so I assumed it was dead and got a replacement. Turns out the original one was still alive and well. Occasionally, they'll move the corals I have sitting on the sandbed around a bit, but nothing too bad. They don't flip them over, just occasionally they burrow in the sand to go under then and shift them an inch or two to the side.