Hierarchy in the African cichlid community African cichlids, even within the limits of a tank, form a hierarchy. After keeping Africans for a while you will see this taking shape. This is true both interspecies and intraspecies. Thus, a male is usually the hyperdominant fish of the tank (which means that it is not challenged by any other fish in that tank AND may crossbreed if given the chance). This fish will usually fight with other males (no matter which species they belong to), will chase every other fish that comes close to it and this is not only done during spawning time. It is more or less a sign of dominance and it calls for a continuous display of its strength. If this hyperdominant fish becomes sick or weakened then another fish will take its place. This is especially true amongst mbuna species and very profound among the most aggressive species. It is strange but once a fish loses its hyperdominant place it is very difficult for it to regain it. Fishes belonging to milder species never take part in this ruling game.
Another hierarchy is present within each species. The dominant fish will display its strength all the time, especially towards rival males of the same species. This is extended to females, too although it takes too much effort and close watching to observe it. In short, it seems that every fish in your tank knows exactly its place in the hierarchy and this will not change unless a fish gains a higher place, always using force to do it. One way to observe it is when you have a sick fish. You will see that this fish is harassed by almost every other fish in your tank. This is not cruelty; it happens in every society. Your fishes are just rearranging their hierarchy and sooner or later the sick fish will reach the bottom of it. Unless treated the fish will surely die either because of the disease or because of the bullying of the other tankmates. The hierarchy is better observed when there is no spawning activity in the tank. When spawning the male will chase any other fish as if temporarily "forgetting" the hierarchy. Immediately after spawning the order is established.
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New additions - reintroducing a fish to the tank Whenever a new fish is added it starts from the beginning, that is from the bottom of the rank. During the first couple of weeks the fish will be chased and usually will not fight back as if checking the existing order of things and see where it could stand. When it gets fully acclimatized it will start to challenge fishes at the bottom of the rank and after climbing some places it will find itself among the others. It is astonishing to see that when a male Maylandia lombardoi challenged my dominant male Melanochromis auratus and won the fight, none of the other M.auratus challenged it. In contrast, when it lost the fight against the hyperdominant Melanochromis chipokae, all other chipokae, including females, fought against it at some time or another (in fact I am not sure who started the fights). After a while it became apparent to the rest of the tank that the place of the M. lombardoi was second to the male M. chipokae only.
The same thing happens when a fish is removed from the tank for any reason and returned after a couple of weeks. It has to re-establish its rank, at least among its own species. Therefore one needs to pay some attention and take certain precautions before introducing the fish back in the tank. This is better done when feeding, thus giving the newcomer a chance to find a hiding place. Another option is to add the newcomer and then turn the lights off. This will also give the fish some time. If you see that a fish is always chased and harassed it it better to remove it from the tank. Such a fish will sooner or later die and may become a life threat for the rest of the inhabitants.
Sodium bicarbonate (baking soda; NaHCO3) - Carbonate Hardness (KH) This is the best kept secret concerning Africans. All you will ever need to have a well buffered tank is sodium bicarbonate (commonly sold in the super market as baking soda). One tablespoon full of it per 150 liters will create a buffer with a pH approximately 8.1-8.5 depending on the starting pH of your tap water and the surface water movement. The stronger the water movement the higher the pH you will get. If you reduce the movement, more carbon dioxide from the air will stay dissolved therefore your pH will drop to 8.1-8.2. I have 6 internal filters (900 lt/h each) and two water pumps (2.300 Lt/h each) creating a very strong water movement so almost all carbon dioxide is released in the air again and my pH ranges from 8.4 (an hour or so after feeding time because of the extra dioxide from the filter bacteria) to 8.5 Since this chemical produces a buffer with the maximum capacity around 8.2 the pH will never drop under normal circumstances (this means provided partial changes are not neglected). This will bring your KH to 11-12.
Please consult the Carbonate Hardness table. In this table you will know what is the content in carbon dioxide for any given pH / KH combination. This table is important because it will show you which is the safe pH range for any given pH for your fish which will also make your live plants thrive. Please note that as much as 40 ppm of carbon dioxide have shown to be tolerated by the fish however, most authors do not accept values over 25 ppm. You will also note the true benefits of baking soda. In very high KH values you will see that addition of too much carbon dioxide doesn't alter the pH of your water significantly. This is very important because carbon dioxide is produced in your tank even if you do not inject it. Another observation is that at pH levels common for African cichlids (over 8.0) the actual content of carbon dioxide is very low. Practically, there is no carbon dioxide at any pH over 9.0
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Calcium carbonate (CaCO3) - General Harndness General Hardness (GH) is a measurement of the content of your tank water in Calcium carbonate. Calcium carbonate is slightly soluble in water and is mainly found in the more soluble calcium bicarbonate [Ca(HCO3)2] form. If you want to know how many grams of calcium carbonate equivalents are in your tank for any specific water volume you should consult the General Hardness Table. This table expresses volumes both in Liters and US gallons for your convenience
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Temperature See also the Temperature Conversion Table
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