You beat me to the punch on escargot shells. That's what I've used with both N. multifasciatus and N. brevis.
Another easy to care for, easily found cichlid is the Bolivian ram. They're slightly bigger than blue rams, much hardier, and more peaceful. Plus, they're very owner interactive. A single or pair would work fine in your tank.
FWIW, and your mileage may vary, but I've found L. curviceps to be much more peaceful than L. dorsigera. The dorsigera I've had have been a bit more on the aggressive side unless the tank is 30" plus in length.
Eric