There are a number of buffers available on the market specifically geared towards African Cichlids, such as Malawi/Victoria Buffer by SeaChem, or Cichlid Buffer by Kent. To maintain a proper alkalinity along with the pH, it's recommended that the water used to dilute these products have a starting pH of 7.0. This can be achieved by using either distilled water or water that has been treated by reverse osmosis.
Using a substrate that's composed either partially or entirely of aragonite will greatly reduce the amount of buffer that will need to be added. Because of the white color of aragonite, it's a good idea to either mix the aragonite with darker gravel, or add the aragonite first with the darker gravel on top. This will reduce the reflection of light off of the bottom and make it more comfortable for the fish.