06-05-2011, 11:57 AM
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I had a look at the report and will try to explain/answer.
Your water is medium hard to hard [GH or general hardness is between 162-298ppm or 9-17 dGH]. KH (carbonate hardness) equates to the alkalinity and is between 86 and 191ppm [equates to 5 to 10 dKH]. The universal measurement for hardness is either "ppm" (parts per million) or "dGH" or "dKH" (degrees GH/KH). We use the European system of degrees in our profiles, I just find it easier to work with. You can switch from one to the other by dividing/multiplying by 17.9, example 162ppm is divided by 17.9 to be 9 dGH, and conversely 9 dGH is multiplied by 17.9 to be 162ppm.
The hardness is the important stuff, as I'll explain momentarily. The pH is usually tied to hardness, and seems to be here, as they give 7.3 to 8.4 as the normal range.
GH is the measurement of dissolved minerals in the water. Calcium and magnesium are the prime minerals for hardness, but others can also affect it. GH does not change in the aquarium, or changes very, very slowly, unless something is specifically added to target it. Example, using lots of wood, leaves, peat will work to soften the hardness by adding tannins. Diluting the water with soft water such as rainwater, RO or distilled water will reduce the hardness. Placing calcareous rock or gravel (limestone, marble, dolomite) or coral in the aquarium will raise hardness as the calcium/magnesium dissolves slowly. But left alone, hardness remains, and regular partial water changes with the same tap water will reinforce this.
GH does affect fish, in that some fish have preferences. Hard water fish need hard water, soft water fish that are wild caught need soft water. Many tank-raised fish manage somewhere in between.
KH is the level of bicarbonates or alkalinity. It is connected to the GH although this connection can be broken, and it buffers pH by resisting any change; there is no need to go into how this works unless one wants to change the hardness. KH has no effect whatsoever on fish, but if it affects the pH that can.
The pH you probably know more about, it is simply put the degree of acidity/alkalinity of the water. A balanced aquarium tends to slowly acidify and the pH lowers, but here is where the buffering of the KH steps in to prevent this. A stable or relatively-stable pH is best, and fluctuations in pH that are drastic or sudden can seriously harm fish. A fish must keep its blood pH equal to the water it is living in, and this takes a lot of energy and the fish can be seriously weakened if the pH is fluctuating wildly. The natural diurnal pH shift of several decimal points is harmless, it occurs in nature and in the planted aquarium. But more sudden or larger pH shifts can be fatal.
As for fish, with your water hard water fish will be perfect. Livebearers, rift lake cichlids, and several species of Cyprinids and some characins will do fine. If your tank pH tends to remain in the low to mid-7's most of the commercially-available fish such as tetra, catfish, Danio, barbs, etc will be fine. Wild caught soft water fish would be problematic.
Hope this helps a bit.