Cichlids like these I mentioned (smaller, less aggressive ones) tend to ignore anything that isn't seen as a competitor, threat, or food.
Cichlids are territorial. They set up a spot and will defend it to the death. In the wild a weaker fish might abandon it for a less ideal spot, but in the aquarium this is not an option, and no matter what you choose one type will be weaker then another. You end up with two pairs fighting over the tank, and at best they will co-exist by being forced into their respective corners and displaying, showing down, or fighting when they meet in the middle (which increases overall stress). This is an unfortunately popular way to keep them nonetheless, but a lot of people think the fighting is 'cool'. I actually agree with this, but I don't think it's cool to subject them to it on a full time basis - I think it's mean.
Now, to use an example, Rasboras are not a threat to Rams because they can't harm the cichlids. They are not a competitor because they don't nest like the cichlids and don't feed in the same manner - they occupy a different space altogether. They're not food because they're too large and quick to be so. The result is ignored Rasbora's, and both types of fish will be able to use the full run of the tank.
The best example I can use, I suppose, is my current 75 gallon with a pair of Nicaraguensis. If I put a rival cichlid in with them they'd have more like 2 feet of space instead of 4, and I can assure you they use all 4. Although they share the tank with a lot of fish, the fish are chosen so that all of the fish can use all of the tank, because they co-exist peacefully. (see below for pics) The tank to me has different dimensions - I still get the character and beauty of the bottom dwelling cichlids, but also have the fast and darty, tight shoaling top dwellers, the nippy, loose shoaling mid dwellers, a nice pleco, and even some catfish that only come out in the evening with the night-light (so I can't get any good pics). Anyway, that's enough rambling and this is just an idea for you to consider, and a way of keeping many cichlids that I think is very underrated.
