They may not all be evil, but mine was. I have a planted community setting with bleeding heart tetras, harlequin rasboras, red eye tetras, zebra danios, and one dwarf gourami. At first when I got my CAE, he was happy with supplemental feeding, but soon I began losing fish mysteriously overnight with no dead bodies to be found. When I got rid of him, the problem stopped. He was only about 4" long at the time.