I have a 55 gal tank with a tiger oscar, two polka dot loaches and a pleco. The oscar and the loaches are about the same size, 2 inches long. The pleco is about three inches. This morning I am missing one of the loaches. It's just gone without a trace. They're usually pretty active and the other one is acting normally. Could the oscar eat the loach if it's the same size? I don't know how else it could have disappeared!