Your Oscars are beautiful and so is their tank.
Weather loaches are some of my favorite fish. A few words on that.... 1) He probably will eventually end up as food as mentioned even at his large size, 2) they require cold water to live their full life spans--warm water shaves roughly 2/3 off their life expectancies--whereas your Oscars like it toasty and 3) they greatly appreciate the companionship of fellow weather loaches. They are one of the few species that can be successfully kept with fancy goldfish.
Everyone looks happy though!