29G is too small for triggers, tangs, puffers etc. However, don't be discouraged. Just like what Fluff said, return the trigger.
I have seen spectacular 29G reef tanks. You can probably spend money on that. However, if you plan on a 29G fish only, I would recommend that you divert your attention to clown, blenny, damsels, etc. The smaller species.
Triggers grow up pretty fast. It may seem tiny at the LFS
but you will seriously consider resizing after a couple of months. And that's more money to require. If you want SW
, look at small fish. Good luck!