04-05-2009, 07:18 PM
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If the disease was ich (white spot), the parasites must find a host fish within 70 hours (according to Baensch/Rhiel) or they die, so if there are no live fish in the tank, they will be gone in that period. If everything else was OK, you needn't pull the tank apart, just clean the gravel, change most of the water, and let it sit. The biological cycling will have to basically restart as there will probably not be enough ammonia to keep the nitrosomonas bacteria alive, and then not enough nitrite for the nitrobacter bacteria. Think of it as a new tank and cycle accordingly.
African rift lake cichlids do best in basic (alkaline) water with some hardness. If your tap water is alkaline and relatively hard, that's a good start, but the biological processes in the tank will gradually lower the pH depending upon the buffering capabiolity of the water (related to the hardness), so you might want to put some dolomite or crushed coral in the filter to keep the pH and minerals up where the cichlids will prefer it. Its been a while since I maintained African cichlids, but a pH of 8 is ideal, or at any rate in the high 7's.