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You're tank might be a bit small for a puffer. You also need to figure out everything that you want in there and add in the least aggressive/territorial order. Check out an Anthias (a lot of unique fish, active swimmers and peaceful). Your LFS will have a few different types.
You should definitely skip the puffer, they need a lot of room and get pretty big. Also, notoriously messy eaters and that would affect your water parameters in a small tank like a 29g. Ours is 6 inches now and does laps in the 180g. Good luck