I have a 10 gallon tank with a 2 1/4" spiny softshell, a small crawfish and five frisky 1"-1 1/2" mosquito fish, all wild caught. So far the turtle hasn't made a move on the fish. At feeding time the little fish manage to get some of the turtle's food. I have seen one of them shadowing the turtle, much like a pilot fish or remora would acompany a shark (or a sea turtle, for that matter). I have seen this same fish grazing bits of dead skin from the turtle's back and even it's neck. Seeing this behaviour in a little aquarium in my bedroom just blows me away.