Microgeophagus ramirezi do best in very soft water, particularly for breeding. while the pH level is not critical within reason, hardness is important. to spur spawning, a conductivity level of approximately 25-125ppm is ideal, though some captive specimens may spawn at a slightly higher TDS.
soft water is also critical for proper egg development. water that is harder has a lower osmotic pressure, compared to the inside of the eggs. water will not flow into the eggs and properly harden them, causing the eggs to turn white and possibly fungus.
East African cichlids such as the yellow lab (Labidochromis caeruleus) do best in hard, alkaline water and are far to rambunctious for the more placid rams. this goes for virtually ALL east African cichlids from lake malawi.