29 gallon aquariums are not very different than the 20 gallon long, despite the almost 50% increase in volume. Floor space (or the footprint of an aquarium) is a major factor in determining which species one can keep and how many of them. Most cichlids keep territories and those territories are along the bottom. Since the 20 gallon long and the 29 gallon have the same footprint, they are very similar as far as stocking recommendations are concerned.
All of the recommendations for the 20 gallon long are applicable for the 29 gallon. Instead of listing those recommendations again, please view them here. In addition to those, we feel that there are 3 more valuable stocking plans worth mentioning.