I have successfully kept smaller Green Terrors with a larger Pike cichlid for years with no issues. This will work as long as your Green Terror is not so small, your Pike can swallow him whole. Your 125g six foot tank gives you the option of going with another Geo or a GT (I think you could do both). Just keep up with regular water changes and enjoy the interactions. Pike are generally much more tolerant of a GT’s antics, then Jack Dempseys who usually get pissed off enough that they eventually stalk, beat up and kill the GT. Good luck and let us know how it turns out.