Bolivian Ram (Mikrogeophagus altispinosus) is probably the best cichlid for community tanks. It is usually very peaceful, particularly so for a cichlid, provided there are no other cichlids present.
It does have a couple things to keep in mind. It is a "substrate" fish in that it remains close to the substrate (mine never get above mid-tank, and that is rare) and feeds from the substrate so it needs sinking foods such as those for cories. This is not a problem, but as you mentioned earlier about wanting upper level fish, I thought I would point it out. The neons will have no issues with the Bolivian Ram, nor vice versa. As for the cories, no problems; at feeding though, since both the ram(s) and cories will be feeding from the same tablets/pellets/disks, it is normal for the ram to do some "pushing" but this never in my experience resulted in injury to the cories. The ram, being a cichlid, will "own" the entire tank space and all other fish will give way (except other cichlids of course).
As for a pair, this works only if a male/female pair and the pair is bonded. This species is believed to live in isolation, except when spawning. The fish have to accept each other--what we term bond--to be successful. I had a pair that did not bond and though they spawned a few times, the male in the end killed the female. In a 30g tank I would say one Bolivian Ram (male if possible, they are a bit more colourful) or a bonded pair.
To get a bonded pair, observe the fish in the store tank for some time, like 15+ minutes, remaining fairly still. Male/female fish will be obvious by their behaviours. Males will continually be "challenging" each other, usually by quick "charges" to another male, rarely coming into contact though they might. Females will not be doing this, but simply hovering around, picking food off the substrate or whatever. The female that is closest to a male, and basically ignored by the male, should be safe with that male.
This fish has a four to five year lifespan. My last single male was into his ninth year when he died a year ago. I will be looking for a new male when I next see a good tank of healthy fish in a reliable store. I do like this species; it has cichlid traits but greatly subdued for a cichlid. I mentioned that the male will own the tank--I had mine in a 5-foot 115g tank of 120 or so characins (tetras, pencilfish, hatchetfish) and cories, but the entire tank was his domain, and the other fish all knew it and respected him. One day the Bleeding Hearts got him annoyed by picking at his food tablet, so he somehow managed to herd them up into the tank, and there they were, in a group of six, being corralled by the Bolivian who was hovering about six inches below them. It was quite obvious from their respective movements that he was keeping them together, out of his way. After several minutes he returned to his tablet but they decided not to venture down to him again. This is one of those instances where not only physical actions are involved, but the Ram was likely sending out chemical signals, allomones, to make his point, and the tetras read them.
Byron.
