Calgary water and Lake Malawi surface waters are remarkably similar, with the only significant differences being that Lake Malawi water is slightly softer, saltier, richer in potassium, and poorer in sulfates. These minor differences are however well within the range of adaptability of any fresh water fish, so no modifications to Calgary tap water is required to keep Lake Malawi fishes. The addition of a small quantity of potassium chloride (e.g. a table salt substitute like No Salt) to Calgary tap water might however be warranted, as this would also be of benefit to plants. Use about 1mL potassium chloride per 100L of water (or 1 teaspoon per 100 gallons).
Calgary tap water is a mixture of Bearspaw and Glenmore reservoir waters. The Bearspaw Reservoir is located on the Bow River immediately west of the city, while the Glenmore reservoir is in the citys south (on the Elbow River). The Bearspaw Reservoir services primarily the north and west of the city, while Glenmore Reservoir services primarily the south and east of the city. The downtown and northeastern parts of the city receive a mixture of the two waters in varying proportions. The output of the two reservoirs is about equal, so their relative distances can approximate their proportional contributions to your homes tap water.
The range in the values reflects their seasonal variations. The actual value on a given day is between the stated limits about 95% of the time. The pH of Calgary tap water is highest in summer, lowest in winter. Sodium and chloride levels in the Glenmore Reservoir (but not Bearspaw) have a sharp peak in March and April when the salt on city streets gets washed away. All other parameters have their highest values in late winter and are lowest in summer.
Hargesheimer, E.A., and C.M. Lewis, 1988, Water Quality in the Glenmore and Bearspaw Reservoirs. The City of Calgary.
Talling, J.F., and I.B. Talling, 1965, The Chemical Composition of African Lake Waters. Internationale Revue ges. Hydrobiologie 50 (3): 421-463.