WATER HARDNESS
PERCH MAN
WATER HARDNESS - essential to grow fish
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Calcium and magnesium, which make up water hardness, are essential in the biological processes of aquatic animals, for example, bone and scale formation in fish.
The critical component of total hardness is the calcium concentration, or calcium hardness.
GH = General Hardness
KH = Carbonate Hardness
GH = dissolved calcium and magnesium
KH = bicarbonates and carbonates, acting as a buffer to stabilize pH.
Total Hardness is the same as General Hardness (GH) but is a more accurate description.
This is a measurement of a combination of both the permanent & temporary hardness.
This is measured with a GH test kit.
Don't confuse water hardness with conductivity.
Conductivity is an indication, but not a way of measuring hardness.
Temporary Hardness is the same as Carbonate Hardness (KH).
It is that part of total hardness that is caused by calcium and magnesium being dissolved by carbon dioxide in water (carbonic acid).
In other words carbonates and bicarbonates of calcium and magnesium. (See note below about inaccuracy of KH test kits)
Temporary Hardness can be accurately measured by:
1. Measure Total Hardness (GH)
2. Then boil the original sample for 15 minutes, cover and allow to cool. (Cover tightly so as to exclude carbon dioxide from the air)
3. Allow any precipitation to settle (or filter it out).
4. Measure GH again. (This second measurement is the Permanent Hardness)
5. Subtract the second reading from the first (Permanent Hardness minus Total Hardness) = Temporary Hardness = (True KH)
Permanent Hardness is caused by salts of calcium and magnesium other than carbonates and bicarbonates.
Measured as described above, it is the GH reading after boiling.
Potential problem with KH test.
It turns out that KH test kits measure total alkalinity of which KH is only a part.
These kits use an acid to titrate the alkalinity in the water sample.
This is usually similar but can be quite different to KH (Temporary hardness)
This fact doesn’t make the test (KH test kit) any less valuable but I only explain this in case the Temporarily Hardness established in the boiled water test comes out different to the KH test.
It goes without saying that measuring TDS, pH, KH and Calcium levels in the various ponds and then doing the above described boiled water test would be extremely beneficial to our understanding of what’s going on.
Common products used in aquaculture
Crushed lime stone
Crushed limestone powder, often referred to as agricultural lime (aglime) or calcium carbonate is a critical, cost-effective tool in aquaculture for water quality management and pond conditioning.
Dolomite
It increases the pH of both water and pond bottoms, neutralizing acidity.
Also see these webpages
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