Most cichlid aggression is to other cichlids, and there are many that work with community fish. The point of fish being stressed out by cichlid aggression regardless of being ignored is a good one, so you don't want anything too skittish.
For example, I tried rasboras, serpae tetras, and congo tetras with my 8" m and 5" F nicaraguensis pair. The rasboras and serpaes are perfectly fine, but the congo's were not happy at all despite being ignored and their superior size, and were removed. Sometimes experimentation is needed.
I don't agree in any way that rams and keyholes are the only cichlids that can be kept like this, I know from experience that many types will work, but I do agree with ferris in this case, considering that it's only a 29 gallon. Perhaps Flags as well. Kribs worked for me but from my understanding it's an iffy choice.
With the exception of keyholes (most docile cichlid available) it really depends on the fish in your tank. It's generally wiser to first choose the cichlid and then choose appropriate fish to go with it. If you have neons, forget anything but the keyholes.
Don't be scared off by negative posts based on what people have 'heard', but do be careful what you mix. If you can give a stocking list of what you have we can help you decide if you can add any cichlids, or what you need to remove or add to make it work.
The same goes for Firemouths and Severums who also get too big for many community fish and would eat small tetra's just because they fit in their mouths
I'd think it's common sense, but obviously the community fish must be suitable size (and there is a suitable size option for any sized cichlid)