Are you looking for stocking suggestions for a new tank, or to add to your current stocking in the 29?
If you are setting up a new 29, I would go with a female Betta Colony. 10 female Bettas in a nicely planted tank. Makes for a wonderful tank.
Or go with 6 female Bettas and 6 Male Guppies. Get one of each of 6 different type of Guppie, the fancier and more colorful the better. We had a set up like this in a 20 gallon tank and it was amazing. So much color, so much movement. No aggression other than during the first week as the female Bettas squabbled amongst themselves while establishing their pecking order.
OBIO