OK, this is the break down. About a year ago I was loosing fish etc. After removing all the rocks from my 55gal and placing them in a wagon for weeks, I finally saw the mantis, he was black and about the size of my pinky finger. Put everything back re-stocked the tank and im hearing the same noise I did a year ago, however Im not loosing any fish. I just bought a 120 gallon I will be setting up in Aug when I move to a new apartment. What suggestions does anyone have for this? Thanks!