I just bought 2 ghost knife(3 inches) in one of my 160 gal tank with 1 pepco(5 inches), 2 Angel's(5 inches), and 2 blue gourami(4 inches). I was gone for about 6 hrs and came back to check on my ghost knife. I don't see them at all and trying to find out who might have ate it. They couldn't have jumped out I have lid on it. Just wondering whom might have ate it. Even check the whole tank remove out plants and ornaments still don't see them. Only conclusion something ate them.