Here are the parameters for the three lakes I compiled from several sources:
Victoria 2-8KH 7.1-9.0pH 98-145cond
Malawi 6-8KH 7.7-8.6pH 6-10GH 210-235Cond
Tang 16-19KH 8.6-9.2pH 11-17GH 606-620Cond
As for me, I don't add salt or buffer, only rely on dolomite substrate to raise the hardness. I do very large water change, about 75%, every two weeks and the steady water parameters are around 12 GH, 4-5 KH, 7.4 pH and 230 conductivity. So my tank parameters are pretty much in line with Lake Malawi except for lower pH. I used to add salt and found my fish scratched a lot after water change and I stopped doing it altogether. Many people don't realize that by adding buffer salt they end up raising GH and KH to adnormally high range even though the pH is closer to the lake range. It is debatable on whehter pH matching or hardness matching is more important.
Also, some cichlid experts suspect that the fine from crushed coral will irrigate the gills and cause scratching. I found that crushed coral is too hard to maintain because they are too light and get finer with time so that it get siphoned off easily. I have replaced crushed coral with dolomite gravel years ago and along with stopping to add salt, my fish have stopped scratching . I suspect that adding salt can lead to parameters swing that can cause more irritation than benefit.
