A dwarf gourami or a honey gourami (even a bit smaller than the dwarf) might do well in your tank of pgymy cories.
Many folks keep them in species tanks. They need brackish water as well, so you might ask down on the brackish forums in a separate thread where you are likely to fnid some folks who own them and have tried various tankmates.losermonkey5 said:if i was going to get figure 8 puffers how many could i get and what would be some good tank mates