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I have had a few different questions about this and thought it deserved a better explanation and to give everyone a firmer understanding and background.
We live in Houston and our water is hard, very hard. Some fish like rift lake cichlids thrive in it, while others from South America and SE Asia fail to thrive or breed. There are many things occuring here and I will try to explain water chemistry, native water conditions, and finally easier manners to set up/maintain a low Ph tank in our city.
Water Chemistry - Many of us see numerous scales and tests for water. We hear our water is hard, but why and what causes it.
TDS - Total Dissolved Solids. This is an actual count of the solids in parts per million (ppm) that is present in our water. It does not tell you what they are, only their presence. Tap water here in Houston is 300-400ppm in my experiance.
Gh - General Hardness. Total or permanent hardness is a measure of the overall concentration of calcium, magnesium and other ions. It's measured in degrees, with one degree equal to about 17.9mg/l (17.86mg/l). The degree symbol is often replaced with a "d" (i.e. 6dGH or just 6dH). The harder the water, the higher the GH number.
Kh - KH - Buffering capacity, temporary or carbonate hardness in the water.
Also known as 'total alkalinity' or 'acid-neutralizing capacity' (ANC) in some countries.
The ‘K’ in KH comes from the German word 'karbonate'. KH is a measure of bicarbonate (HCO3-) and carbonate (CO32-) ions that act as buffers in the water to prevent the pH dropping or changing sharply (especially at night if you have plants in the aquarium). One degree KH is equal to 17.9 mg/I (ppm) CaCO3. It's also measured in degrees. The degree symbol may be replaced with a d (ie. 2 dKH).
A common misconception is that KH is a part of GH and that KH cannot be higher than GH. There is no such correlation. In some areas, the water contains more sodium bicarbonate and/or potassium bicarbonate than total calcium and magnesium. In these areas, the KH is naturally higher than the GH. Furthermore, people using water softeners will most likely have a KH that is higher than the GH, as water softeners exchange sodium or potassium ions for calcium, magnesium, and other hard water minerals.
Ph - pH is short for the Latin phrase pondus Hydrogenii or the 'weight of Hydrogen'.
(often incorrectly labelled the 'potential of Hydrogen' or the 'power of Hydrogen')
Commonly said to be a measurement of how much acidic or alkaline water is.
pH is the measurement of the weight or amount of hydrogen (H+) and hydroxyl (HO¯) ions dissolved in water. It is the balance between the weight of these two types of ions which determine its pH value. In pure or distilled water these ions are in balance. H ions in a litre of pure water will weight 10-7 grams or 0.0000001 grams. So this figure is used to express the pH value.
However for ease of use it has been the convention of the chemistry profession not to write the whole number and to ignore the negative value and just write '7'.
In the natural world, pure water falling from the sky as rain water very quickly absorbs dust and other particles from the environment and so this unbalances the ratio of the two ions. The balance can either increase or reduced the ratio of Hydrogen to Hydroxyl. This unbalance is a very important chemistry measurement and is expressed in two terms.
These things are interconnected and A high GH or Kh will result in a higher TDS or vice versa.
How to apply this to aquariums. Soft water from SA or SE Asia is bereft of most minerals (TDS > 50ppm or even less, no Gh or Kh) and filter through rotting plants and pick up tannins which drop the Ph to low levels. I have seen field cases of Ph being below 4.0. To have a Ph this low we must first remove all minerals from the water. Distilled or RO water are a must. Now we are at Ph 7.0. Now we must introduce something that will add tannins or introduce carbon dioxide (which produces carbonic acid) and this will lower the Ph of the water. Driftwood and peat are effective in this regard as with Indian Almond Leaves and Alder Cones. Ph reducing substrates can help as well such as Aquasoil, Stratum, or Brightwell. These help in stabilizing a low Ph environment, though they are not necessary. We must be careful not to add any substrate or rock that will leach off minerals in this acidic environment. Holey rock and Aragonite sand are limestone and will shed its minerals to an acidic water, increasing Kh and TDS. Once the tank is stabilized, we must consider our Nitrogen cycle. This functions well in higher Ph high mineral tap water, but the bacteria cease to live below a Ph of 6.0 and is progressively better as the Ph increases. Ammonia no longer breaks into Nitrite, but becomes Ammonium in this acidic environment. Ammonium is far less deadly, but will register as Ammonia as the tests do not differentiate the two. This is the factor we are watching for setting our water change schedule. Plants can uptake this as well, instead of Nitrates like a harder water tank. This environment is devoid of most bacteria and fungus, thus these fish have evolved for countless thousand years. The fish can survive in harder water, but breeding is much more effective in this type of situation and reproduction of their natural habitat. Their eggs and linings have not needed to resist bacteria and fungus, so they have not adapted to it.
I have given a lot of very hard science in this, but the better we understand these criteria and issues, the better off we are at overcoming them. It is not easy to decide upon a soft water tank, but they are rewarding. Imagine spawning Cardinal tetra or a rare Apistogramma or Ram and seeing them thrive. They are all achievable here, it just takes knowing your goal and how to best achieve this. I know I missed a few things, so I'll try and update with more as I remember and answer any questions anyone has. I'll link this to a few facebook pages and please post questions here so everyone can hear and see any advice or problems that might occur and share with the community our knowledge.
We live in Houston and our water is hard, very hard. Some fish like rift lake cichlids thrive in it, while others from South America and SE Asia fail to thrive or breed. There are many things occuring here and I will try to explain water chemistry, native water conditions, and finally easier manners to set up/maintain a low Ph tank in our city.
Water Chemistry - Many of us see numerous scales and tests for water. We hear our water is hard, but why and what causes it.
TDS - Total Dissolved Solids. This is an actual count of the solids in parts per million (ppm) that is present in our water. It does not tell you what they are, only their presence. Tap water here in Houston is 300-400ppm in my experiance.
Gh - General Hardness. Total or permanent hardness is a measure of the overall concentration of calcium, magnesium and other ions. It's measured in degrees, with one degree equal to about 17.9mg/l (17.86mg/l). The degree symbol is often replaced with a "d" (i.e. 6dGH or just 6dH). The harder the water, the higher the GH number.
Kh - KH - Buffering capacity, temporary or carbonate hardness in the water.
Also known as 'total alkalinity' or 'acid-neutralizing capacity' (ANC) in some countries.
The ‘K’ in KH comes from the German word 'karbonate'. KH is a measure of bicarbonate (HCO3-) and carbonate (CO32-) ions that act as buffers in the water to prevent the pH dropping or changing sharply (especially at night if you have plants in the aquarium). One degree KH is equal to 17.9 mg/I (ppm) CaCO3. It's also measured in degrees. The degree symbol may be replaced with a d (ie. 2 dKH).
A common misconception is that KH is a part of GH and that KH cannot be higher than GH. There is no such correlation. In some areas, the water contains more sodium bicarbonate and/or potassium bicarbonate than total calcium and magnesium. In these areas, the KH is naturally higher than the GH. Furthermore, people using water softeners will most likely have a KH that is higher than the GH, as water softeners exchange sodium or potassium ions for calcium, magnesium, and other hard water minerals.
Ph - pH is short for the Latin phrase pondus Hydrogenii or the 'weight of Hydrogen'.
(often incorrectly labelled the 'potential of Hydrogen' or the 'power of Hydrogen')
Commonly said to be a measurement of how much acidic or alkaline water is.
pH is the measurement of the weight or amount of hydrogen (H+) and hydroxyl (HO¯) ions dissolved in water. It is the balance between the weight of these two types of ions which determine its pH value. In pure or distilled water these ions are in balance. H ions in a litre of pure water will weight 10-7 grams or 0.0000001 grams. So this figure is used to express the pH value.
However for ease of use it has been the convention of the chemistry profession not to write the whole number and to ignore the negative value and just write '7'.
In the natural world, pure water falling from the sky as rain water very quickly absorbs dust and other particles from the environment and so this unbalances the ratio of the two ions. The balance can either increase or reduced the ratio of Hydrogen to Hydroxyl. This unbalance is a very important chemistry measurement and is expressed in two terms.
These things are interconnected and A high GH or Kh will result in a higher TDS or vice versa.
How to apply this to aquariums. Soft water from SA or SE Asia is bereft of most minerals (TDS > 50ppm or even less, no Gh or Kh) and filter through rotting plants and pick up tannins which drop the Ph to low levels. I have seen field cases of Ph being below 4.0. To have a Ph this low we must first remove all minerals from the water. Distilled or RO water are a must. Now we are at Ph 7.0. Now we must introduce something that will add tannins or introduce carbon dioxide (which produces carbonic acid) and this will lower the Ph of the water. Driftwood and peat are effective in this regard as with Indian Almond Leaves and Alder Cones. Ph reducing substrates can help as well such as Aquasoil, Stratum, or Brightwell. These help in stabilizing a low Ph environment, though they are not necessary. We must be careful not to add any substrate or rock that will leach off minerals in this acidic environment. Holey rock and Aragonite sand are limestone and will shed its minerals to an acidic water, increasing Kh and TDS. Once the tank is stabilized, we must consider our Nitrogen cycle. This functions well in higher Ph high mineral tap water, but the bacteria cease to live below a Ph of 6.0 and is progressively better as the Ph increases. Ammonia no longer breaks into Nitrite, but becomes Ammonium in this acidic environment. Ammonium is far less deadly, but will register as Ammonia as the tests do not differentiate the two. This is the factor we are watching for setting our water change schedule. Plants can uptake this as well, instead of Nitrates like a harder water tank. This environment is devoid of most bacteria and fungus, thus these fish have evolved for countless thousand years. The fish can survive in harder water, but breeding is much more effective in this type of situation and reproduction of their natural habitat. Their eggs and linings have not needed to resist bacteria and fungus, so they have not adapted to it.
I have given a lot of very hard science in this, but the better we understand these criteria and issues, the better off we are at overcoming them. It is not easy to decide upon a soft water tank, but they are rewarding. Imagine spawning Cardinal tetra or a rare Apistogramma or Ram and seeing them thrive. They are all achievable here, it just takes knowing your goal and how to best achieve this. I know I missed a few things, so I'll try and update with more as I remember and answer any questions anyone has. I'll link this to a few facebook pages and please post questions here so everyone can hear and see any advice or problems that might occur and share with the community our knowledge.
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