It's basically just a big aggressive wet pet, definitely couldn't have anything else in with one in a 125/140. 24" max though I believe most max out at about 20".
Pair of Jags maybe? Even that's pushing it though.
Could do a basic central mix with Salvini/JD/Firemouth. What sort of decor do you run in your other tanks, I prefer natural tanks so I keep it to at least sub-continental stocking.