I have a 135 gal tank. I had an Oscar about 5”, a Jack Dempsey about 2”, and a Green Terror about 2” thats been in the tank for a couple months. A week ago I added about a 2” red terror, about a 3” chocolate and red shoulder severum. While there are no visible signs of a parasite and they eat like hogs, I do occasionally see scratching from the Oscar and red terror. Nothing constant. Every once in a while. And it isn’t like multiple rubs at one time. Just a scratch and go about their business. I also notice the Oscar tends to flick his little pelvic fins when fish get close to him. I just checked my ammonia, nitrites, and PH. All seems safe amounts. What are y’all thoughts? Parasite or marking their territories?