# gh kh



## finfollower (May 27, 2004)

hey guys, i'm just wondering if there is an ideal gh or kh for plants or just like a range which most plants are likely to fall under.


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## Zapins (Jul 28, 2004)

Most plants do very well in relatively hard water (high gH). I kept all plant species in water with a gH of 17 degrees, but now i have a gH of 9 and plants do fine as well. Plants aren't too picky when it comes to gH, just as long as there is more Ca in your water then Mg

kH is more up in the air as to what grows everything. IMO a kH of 4-5 is fine, but other people like it lower. Again plants aren't picky when it comes to this so you won't have to change your tap water.


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## BryceM (Nov 6, 2005)

I'd say that any GH over 4 or 5 degrees (100 ppm) will supply enough Ca and Mg for almost every species. Usually both Ca and Mg will be present in reasonable proportions, but sometimes Mg is low. KH is not critical, but most people prefer at least 3 to provide a bit of buffering. Getting a correct GH/KH is probably more important for the fish than the plants.


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## finfollower (May 27, 2004)

how do you increase or decrease gh and kh?


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## BryceM (Nov 6, 2005)

Raising either is easy. Lowering either is not.

To raise GH, you need to dissolve more calcium or magnesium. There are many ways to do this. You can use pre-mixed products like Seachem Equilibirum or Greg Watson's GH booster which will provide both Ca & Mg in the correct proportions. You can also dose dry chemicals like Calcium Chloride (CaCl2) Calcium Carbonate (CaCO3), or Calcium Sulfate (CaSO4). Magnesium is usually added by using epsom salts, almost pure MgSO4-7H2O. Most of these are dirt cheap and Greg Watson or other chemical suppliers sell plenty of whatever you're looking for.

Raising the buffering capacity (or KH) is usually done by adding baking soda (NaHCO3). The sodium from this is theoretically harmful, but in the amounts most people use it's apparently not a big issue. Some people have started using KHCO3, but it's harder to find.

The only feasible way to lower GH or KH for most people is to use a reverse osmosis filter (RO). Peat is sometimes used but it is very slow and adds lots of tannins to the water. Some plants (Valisernia sp) will slowly deplete carbonate (KH) since they use this as a carbon source. The final option, which is useful only for nanos, is to mix tap water with distilled water to provide the desired GH or KH.

My tap water is KH <1 and GH 2-3 (German degrees). I add 1 tbsp of Seachem Equilibrium and 1 tsp of NaHCO3 per 20 gallons at water change. I usually end up with a KH of 4.5 and GH of 5.


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