i think 2 in a 75 is a little over kill, i would remove one, not sure if there wil be enough food for 2 to live. i have one in my 57 for 15 months now and he keeps the sand clean. it doesn't move much during the day and once i did have to move the rock to see if its alive myself because he didn't move for a week other times i see him moving around the whole tank