Tahitian Mood Sand provide texture, color and pH buffering
The African Rift Valley is currently expanding at approximately two centimeters per year and may very well be the beginnings of a new inland sea. Lake Malawi is approximately 50 Km wide by 600 Km long and is located immediately southeast of Lake Tanganyika, which is approximately 40 Km wide by 750 Km long. Lake Victoria is approximately 350 Km to 410 Km in diameter and is located northeast of Lake Tanganyika. Incidentally, Lake Victory is the third largest lake in the world and is the largest tropical lake in existence. The average temperature of 76-80F can be found in all the lakes with extreme seasonal temperatures varying from 70F to 86F. Because of constant, geological expansion over time, in a relatively stable environment, there were ample opportunities for general riverine newcomers to colonize and specialize. There are now hundreds of endemic cichlid species, which have evolved into behaviorally complex, beautiful colored and highly specialized fishes, living in a wide variety of habitats. The cichlid family of fishes is known as the "Darwinian Finches" of the lakes.
Mineralization and salinization of the water has also occurred. Seasonal rains leach salts from mountains and other geological formations, thus raising the dissolved salt concentration over time. Currently Lake Tanganyika has approximately 1.5 grams of salt per gallon, German hardness of 12-14 and a pH of approximately 9.5. The salt concentration of Lake Malawi and Victoria are one half and one third respectively with a pH range between 7.8 and 8.5. The lower salt concentrations of these two lakes provide evidence of their age and indicate Lake Victoria as being the youngest of the three. Cichlids have a distinct physiological advantage over other riverine species when it comes to living in this environment. It is their tolerance to high salt and pH, which allows them to out compete other species, which are better adapted to living in the softer, acidic waters found in rivers and swamps.
