08-25-2009, 12:36 PM
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I've been dealing with this recently, as I am now adjusting the hardness of my aquaria water. My tap water is zero, as soft as it can be, and I think the mineral balance of the fish needs to be considered.
GH is general hardness, caused primarily by the amount of calcium and magnesium in the water. It is expressed in either dGH [degrees of GH] or as ppm [parts per million]. API test kit gives it as ppm, and you convert by dividing the ppm by 17.8 to get dGH, or if you have dGH you multiply it by 17.8 to get ppm. So 53ppm is approximately 3 dGH for example.
KH is carbonate hardness [carbon is karbon in German, hence the "K"] and refers to the level of carbonates in the water. These can affect pH or attempts to adjust pH, as they are the buffering agents.
The easiest way to add hardness and raise the pH is with dolomite, limestone or crushed coral. I have in the past done this for livebearers and for a tank of rift lake cichlids, with success. Dolomite is a type of gravel that "dissolves' slowly adding calcium to the water. It works for months if not years. Best way is to put an amount in a nylon bag in the filter; it is easier to control the amount in this manner, rather than mixing it in the substrate gravel.
First question is, what is the hardness and pH of your tap water? Once you know this, you decide how much dolomite may be needed to raise the hardness/pH to where you want it, and I agree, pH of 7.5 is perfect for livebearers. What was the KH and GH after treatment? When you have these numbers (tap water and tank water pH and hardness) I can offer further suggestions.