so I have a juvenile tiger oscar in my 150 gallon tank, and just recently put in 2 upside down black catfish. The oscar is about 1.5 inches long, and the catfish are about 2.5 inches long... After putting them in the tank together, I've noticed my Oscar acting lethargic and his tail is a little worn... It could have been that way since I got him, but I'm pretty sure it hasn't. Is this a serious issue of compatibility, or is my Oscar just sick? Any help ASAP would be appreciated!