Other important question that has not been asked, what species or trigger, what size tank, and what size trigger?
A 2" Niger or even a Clown can go with lots of fish, but a 12" Clown can kill an entire tank out. Other BAD triggers (Undulated, Black Hawaiin) these will not do well with any other fish in a small/med tank.
So you need to do some homework. Also is this reef (shrimp, crabs, snails)? If so that limits you even more.