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Hello all, i have recently been looking into creating correct water parameters. The only one seemingly causing me problems is KH. I just tested my water this evening after reworking my tank and my Kh is still about 200ppm or thereabouts. How can i go about lowering this parameter because i believe it might be why my plants have not been growing. All other parameters are good other than my ph is a little high at 7.8.
 

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Hello all, i have recently been looking into creating correct water parameters.

All other parameters are good other than my ph is a little high at 7.8.
What is your local tap water?
IMO stay close to it if at all possible.
Have you tested your Ca?
What other parameters are good?
 

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Discussion Starter · #3 ·
everything in my tank is tap water actually. i test the water prior to and after water changes and the tap water itself and the parameters are all the same. no clorines or chloramines, nitrates are minimal no nitrites, and my water runs soft.
 

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Reverse osmosis is by far the easiest and most reliable method.

If you're prepared to prep the water and play a little chemistry, citric acid will work well.
 

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There are a couple of ways to lower KH. In turn, this will usually lower the pH.

1) Blend your tap water with reverse osmosis or distilled water in the % by which you want to lower the KH.
If you want KH to be 100ppm (50% of its current value) then blend 50/50 RO + tap. You may then have to correct the GH, if the tap water already has a low GH.

2) Find a media that will remove KH from the water, and treat the water with this. One such material is montmorillonite clay such as Safe-T-Sorb, Turface and related materials. If you can filter the water through this, a lot of the KH will be removed, but IME the GH will stay the same.
I have seen the effect of using STS and other montmorillonite clays as a substrate in aquariums and it removes a lot of the KH. It can also cloud the water, so I would suggest rinsing it first, then filling a canister filter perhaps 2/3 with STS, and the last basket with floss to remove the remaining fines.
Example: in a tank that holds 88 gallons of water, 2" of substrate represents about 10% of the volume, this substrate kept crashing the KH from tap water and from baking soda or potassium bicarbonate for over a month. Every few days I would raise the KH to about 4-5 German degrees of hardness (roughly 70-90ppm) and it would be back down to 0 the next day.
Similarly, a standard 29 gallon tank, 2" of substrate is also about 10% of the volume. In this tank I was not correcting the KH as frequently (only about once a week) but it went on for over a year, dropping to 0 in between additions of baking soda.
 
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