My first and strongest suggestion is "don't". In a 29 gallon tank, which is taller than it is wide, those fish are going to have major issues almost from the start. Even starting with small, young fish, between agression levels, territorial habits, and simple space for swimming, not to mention water quality... all going to be deadly in that size of a tank with that mixture of fish.
Would you consider something different for fish if that is the only tank you can provide? If you're stuck on those fish, you're going to need about 90 - 125 gallons just for what you have listed... if you want it to work... and tons of rockwork and other decorations and lots of water changes.
If you're really want to work in that size of a tank, there are better options while staying with that same category of fishes. The African Cichlids also have quite a few that are small shell dwelling fish, and they're a lot of great fun to watch. In 29 gallons with lots of shells and decorations, you could get probably about 6 - 8 of them in there comfortably, though I would still nix the idea of a pleco. Can I ask why the need for a pleco in an African cichlid tank? African cichlids are heavy vegetarians, and will typically eat all plants and most algaes that grow other than slime algae. If the water quality is good and the fish aren't overfed, there should be no slime algae buildup. I have 11 tanks running right now, and the only thing I ever have to scrape is the hard water deposits from evaporation. In 90 gallons I keep one juvenile rubber nose pleco, about 3 inches long... and there are over 100 mollys in that tank (most fry), yet I have never in the past year had to scrape it once. Algae problems are typically an indication of the water quality and lack of enough maintenance to the tank, and even over feeding. If you tank is healthy, you won't need the pleco, and since it can't stay in a 29 gallon beyond a few months, it would be pointless to put it in there to begin with.
Nobody can stop you from doing what we all can see is going to be a huge problem soon, but we can ask you nicely to please not do this. This is cruel. Adding those fish to a 29 gallon tank would be like locking you and your entire family into a closet together, forcing you to do everything for your daily needs right there... eat, sleep, defecate, etc. You could probably survive in there for a short time, as your fish maybe can in that tank, but soon enough the conditions would become toxic, you and your family members would get sick, and eventually die if left there like that. The situation for your fish is no different. Its great that you want to keep fish, take good care of them, etc... but in doing all of that, don't you first have to be real and honest about what is possible and what is not? Putting a fish that gets 5 - 6 inches long into a 29 gallon tank with so many others just as large and aggressive isn't taking proper care of them, or providing for their needs.
If you need other ideas for what will work long term in a 29 gallon tank, please, just ask. I have a whole list I could make for you, and I'm sure others here could easily add to it. Doing right is the important thing, yes? Much larger tank or different fish, that is the only way to do right here.
