I have a 200 gallon tank set up, with some 6-7" rays, 4 clown loaches and a couple of silver dollars. I just noticed one of the silver dollars looks like a fish has been chewing on him. I can see the loaches picking on the wound. Anyone else have this happen? Is this normal for loaches to attack a silver dollar? the loaches are 3-4" long. Silver dollars are around 4" long.