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what is best way to lower carbonate

Canberra Alex

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ok sorry for the delay

from the tap = KH is 4 and GH is 2

in the tank = Kh is 13 and GH is 7

one day after water change

i would like to keep the KH at around 8 and the GH at around 5-6 there something i can do to get it and keep it low?

the tank is 235l and has DIY CO2.

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What substrate and rocks do you have? Any limestone, crushed coral marble chips etc? Sounds like there is something in the tank pulling it up.


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This is part of an article I wrote...it may help you...

How to Soften Water which is too Hard

The ideal solution is to collect rain water and dilute it with tap water until the desired hardness is obtained. Unfortunately, this method requires various precautions and involves certain risks. The guttering and storage tank must be of non-metallic material. They must be as clean as possible, and cemented roofs must be avoided (essentially cement is powdered limestone). This activity cannot be carried out in regions where the atmosphere is highly polluted because the rain will contain all sorts of unsuitable elements. Water collected close to or downwind of, industrial areas may be polluted. Collect only during prolonged downpours, and wait a few minutes while the dust and any other rubbish is washed away. It is highly advised to filter or strain the collected water through filter wool to remove any detritus.

Boiling water will remove some, but not all, of the dissolved salts

You can also pass the water through resins, which capture the mineral salts and leave it very soft. This method, which is known as ion exchange, requires a well regulated flow of water and the resins to be changed regularly (use only resins sold for aquarium use). This may affect the pH, and, as it exchanges calcium ions for (usually) sodium ions, the result may be soft but still mineral-rich (and unsuitable for fish from mineral-poor regions).

In recent years a technique called reverse osmosis has been made available to the hobbyist. This involves utilizing a unit to produce water which is chemically pure, hence perfect for aquarium use. This removes all minerals but it is wasteful – some 45.5 litres of tap water are needed to produce 4.5 litres of mineral-free water. It cannot be used alone because when devoid of all its salts, the water becomes very unstable. The pH can then fluctuate widely in a short space of time, becoming dangerous for the fish. Also, the process involved in the removal of minerals, removes free oxygen, so there is nothing to “breathe”. It must be aerated heavily before use, and never used “neat”. However, the greatest drawback of this process lies in its high cost.

Finally, it is also possible to use a very soft bottled mineral water, either for dilution or for the small tanks used to breed fish.

However I agree with Dean...I think something in the tank must be raising the hardness.

Andrea smile.gif

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If you're using C02 I will assume this is a planted tank. I have very hard tap water so I feel your pain. I find Seachem acid buffer great to lower hardness. It is really potent stuff and you only need a small amount. Acid buffer is good because it also raises the amount of dissolved C02 in the water.

Peat, as has already been suggested, also does the trick however has a nasty habit of turning water a bit brown.

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