It's only a 29gal folks. Don't recommend med to large sized puffs. Their appetites alone make a 29 too small.
A good choice for an active full-FW puffer would be the Asell's puffer or Peruvian puffer Colomesus asellus. These puffer are always on the move, peaceful towards each other, and not skittish once they're used to their environment. Give them a clean planted tank with some caves or overhangs and these puffs will live for 10 years and reach 3". They'll feed on live/frozen worms, snails, and small crayfish. Provide something to eat that'll help keep their beaks shaved down.
With good filtration, you can keep 3-4 of these puffs in a 29. I have a 55 with 8 Asell's puffers and 8 dwarf puffers. I have yet to see the 2 species bicker. If anything the dwarf puffs show the most aggression but, only amongst themselves.
Palembagensus and miurus are OK if you don't want to see much movement.