I've had my pair (at least they act like a pair) for going on 3 years. It's been very entertaining watching them interact. They are rarely more than a foot or two from each other, the exception being at feeding time. One interesting thing that I've noticed with them is that they will change their color and pattern to signal one another. The change happens within a matter of seconds, and is usually followed by touching or a brief chase around the pool.
Here's a pic of them doing a color and pattern change. They have other configurations as well, but this is the most common. After a few minutes, they'll go back to normal.
Here is how they look 90% of the time.
I had an incident last year when one of my triggers turned to the dark side and chewed one of their tails down to the caudal peduncle (Trigger was rehomed of course). While the puffer that had it's tail bitten off laid at the bottom of the pool recovering, the other one would not leave it's side. It would constantly rest on top of or directly next to it's injured buddy. Not sure if it was for protection, or to take advantage of an opportunity to establish dominance, but it was very cute. For almost an entire month while the injured one was recovering, the other one wouldn't even leave to eat. I'm happy to say that the injured fish is now completely recovered, minus a bit of it's caudal fin.
This one got a NLS pellet stuck on one of his spines, and swam around with it attached for a good 30 minutes.
Here's a pic of one of them doing it's speedboat impression across the pool thinking it's feeding time.
Anyway... it's definitely worth a shot trying to keep a pair together. Based on my experiences, I would give you pretty good odds given the size that you are considering adding them at (Mine were both around the 2" mark when I got them). You might want to try an acclimation box or tank divider at first to let them get used to one another.
Good luck, and keep us posted!
I love it!
