120 cichlid tank?

[dorkfish]

god, both your tanks are crowded/overstocked.

 

[langlin]

not so fast Chief.

Nope, blue dempsey are South/Central American, you'd have problems, it also grows to a size that would make the rest of your fish become food

It's not the size of the dog in the fight, it's the size of the fight in the dog!
If you put Melanochromis species in that 120, a Dempsey will have his fins full.
however, i don't recommend you mix mbunas with Central American Cichlids.