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I recently had cause to ask an online African Cichlid expert for advice on breeding a particular Lake Victoria haplochromine. I described my setup along with pictures. The tank I was (and am) using was a leftover from some South American cichlids and featured driftwood and large non-carbonate rocks. He ventured the opinion that I had the wrong sort of biotope, Lake Victoria being a Rift Lake and having therefore extensive reefs of rock. I had not gotten that impression, so I set about to try to find out what the actual topography is of the bottom of Lake Victoria. This proved to be a difficult search because so much bandwidth is dedicated to decrying the ecological disasters that man has caused in Lake Victoria that it is difficult to locate anything else. Eventually, however, I found enough information to satisfy me.
According to Dr. Robert J. Goldstein, in Cichlids of the World (pages 350-354), Lake Victoria is situated on a plateau between two arms of the Great Rift Valley, and is formed from flooded plains which have been deformed between the two. The maximum depth is 270 feet and the average depth is 140 feet. It is only the most recent of several generations of lakes which have formed in that location as the plateau lifted and tilted in response to the geological forces at work in the Rift Valley. The bottom of the lake is sand, covered with mud in the shallower regions. The water annual rainfall into the lake is 1,260 mm, the annual inflow from rivers and streams is 330 mm. 1,310 of the 1,590 total mm of new water each year is lost by evaporation. One gets the impression of a large mud puddle. Photographs of the countryside surrounding Lake Victoria can be found at Corbis Stock Photography and Pictures. The surrounding geography is that of rolling hills with occasional outcroppings of rock. Contrast this with pictures of Lake Tanganyika, with the shorelines of sheer limestone tumbling into the water, and you will see why I do not believe that the Lake Victorian haplochromines require a reef-like biotope similar to that of the Rift Lake species.