I have heard from many people and read in books that the african cichlids are from brackish water but I know it's not necessary to have it, like I said I did it for better coloring and it seems to have made a difference...I found this online, its a good guide for water chemestry for different types of cichlids
Water Chemistry of the African Great Lakes
Chemical ConstituentL. VictoriaL. MalawiL. TanganyikaElectrical conductivity
(µS = µmho)91-145210-220606-620Total solids
(mg/L)76-118—460Sum of cations
(meq/L)1.04-1.212.457.30-7.46Sum of anions
(meq/L)1.08-1.772.5-2.597.25-7.71pH
8.0-8.88.5-8.6
8.66-9.06*Na (sodium)
(mg/L)10.4-13.521.057-63.6K (potassium)
(mg/L)3.7-4.26.418.0-35.5Ca (calcium)
(mg/L)5-1516.4-19.89.2-17.6Mg (magnesium)
(mg/L)1.59-84.7-8.839.2-43.3HCO3 + CO3 (bicarbonate,
carbonate) (meq/L)0.25-1.532.36-2.586.02-6.81Cl (chloride)
(mg/L)3.9-7.03.57-4.320.9-36.6SO4 (sulfate) (mg/L)
(using ion-exchange resins)2.35.57.2-15.3SiO2 (dissolved silica)
(mg/L)3-201.1-40.3-6.6NO3 · N (nitrate-nitrogen)
(µg/L)11-29—below detection
limitPO4 · P (phosphate)
(µg/L)3-13<7-307Total P (phosphorus)
(µg/L)47-67—[21 (doubtful)]