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Other Methods Of Reducing Hardness

By James Montgomery


here are other methods of reducing hardness and I have mentioned the use of Ion-Exchange Resins. These exchange sodium for calcium and magnesium and thus increase the sodium content of the water. Although this practice is becoming more common I am doubtful that the increase of sodium is desirable so I do not use it. The method described above is that based on what takes place naturally in the wild and so I will keep in line with Mother Nature who seems to have done a good job for a long time. No mention has been made to the correction of carbonate hardness or KH. This is because I have generally found that the above process tends to adjust the KH at the same time and the only problem may be if it falls too low. Some KH is required to act as a buffer against the normal conditions in the tank. I suggest a final KH test, If this falls below 2 oKH this may be adjusted by the addition of a small amount of Sodium Bicarbonate preferable dissolved in water previously. A final result of 2-4 KH is desirable. You will notice I have not mentioned a target to aim for when making an adjustment. This can vary with the species to be maintained and detailed information can only be found by consulting the specialist books on the subject. As a general rule I would say that if you obtain a reading of 6.8-6.9 PH and about 5.5-7 GH you will not be too far out as a general rule. As I mentioned fish are fairly adaptable and this range will be found suitable for most of the Anabantoids from S.E.Asia though those from Africa may prefer slightly harder and and more alkaline water.


Since at present you probably have your fish in normal tap water another word of warning is called for. Although we are aiming for ideal water conditions your fish should not be transferred into a new tank of water containing your ideal mixture. Your fish have become adapted to the qualities of your tap water and a sudden change from this will do more harm than good. There are several ways of carrying out a gradual adjustment but I think that the easiest is by finding out your correct mixture as detailed above and then carrying out a weekly water change, siphoning off about 10% of the tank water and replacing it with the new mixture. Keep a check on progress by carrying out a water test the day after after doing the water change, this will allow for a thorough mixing of old and new water and give a reliable result. If you treat all your tanks in this way you will have no problem in setting up a breeding tank as your fish have already adapted themselves to the water quality involved. Remember that when adding water to a tank it should be at the same temperature as that in the tank. The other necessary warning is to avoid the danger of becoming a PH fanatic. You will find that you take a reading from a sample of tank water at sundown and another at dawn they may vary due to the process which is used by the plants in your tank. During daylight they give off oxygen but darkness this changes to Carbon Dioxide. As this gas is slightly soluble it means that the tank conditions at dawn following a build up through the night, will be at their most acidic.


While at sunset reverse conditions will be found. This is a normal state of affairs and should cause no alarm. What can cause trouble is if one tries to correct these small changes and thus upsets the natural balance in the tank. If possible it is a good habit to carry out any necessary tests at the same time of the day and therefore at the same tank conditions in this respect. Once your tank is set up continual monitoring is not necessary. The best guide will be the condition of your fish. If they show good colour, are active and feed well there is little wrong.


I think that once you have established these conditions this will be the case and you will find that the slight amount of work and inconvenience involved in producing them has been worthwhile. lt is always a good idea to make a record of how tanks are set up and any changes made. The use of a note book for this purpose is recommended. In this way a useful reference can be built up, especially if later one wishes to refer to the conditions under which a species has successfully bred.


Suppose for example you found that it took .5 peat water and 1.5 to produce the desired result,you now have a permanent record of the proportions required to carry out the necessary adjustment of your tap water as this remains fairly constant. You know that two pints of water, 5 pint of peat water and 1.5 pints of plain rainwater produce the correct mix of 4 pints of aquarium water. Thus for a 20 gallon tank, 160 pints,you would need 80 pints of tap water, 20 pints of peat water, and 60 pints of plain rainwater. This record not only can be used to set up future similar tanks but also gives the required mixture to be used when topping up your tank while carrying out normal water changes. Thus a quarter of an hour spent in taking a few Careful measurements and recording them will save you the hassle of having to go through this procedure each time.


Perhaps I should mention that the results may not be exactly the same each time that you carry out an adjustment but the resultant mixture will only vary slightly and will be near enoUgh for our purposes. In the unlikely event of you finding that your tap water is too soft and acidic the adjustment can be carried out by the use of hard alkaline solution made from dissolving dehydrated Lime. This again may be obtained from a garden centre but make sure it contains no other chemicals. Put a few pounds into your container and then fill with rainwater and allow to stand for a week before use.

I am old fashioned and work in pints and gallons, for those who prefer to work in Litres a conversion table is found below.

1 x Imperial Gallon = 4.5 Litres of Water.
1 x Pint. = 0.87 Litres.
1 x Litre. = 0.22 Imperial Gallons.
                   1.76 Pints i.e. aprox. 1¾ Pints.



This article first appeared in the Greenock & District Aquarist Society newsletter "The Angelfish" January 1996. no 5. and is also duplicated on the Help index on Water Chemistry


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                                                                                                              Article updated = February 2, 2018
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