pH and kH confusion - The Planted Tank Forum
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post #1 of 5 (permalink) Old 12-04-2016, 01:37 AM Thread Starter
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pH and kH confusion

My tap water here in Boston comes out of the tap at 8.8 with a kH of 1.2. The pH of my tap water left sitting for 24 hours drops to 7.53 and kH remains around 1.2. My tank currently is 7.44 with a kH of 2.65. My question is how do I increase the kH of my tap water for water changes or is it even necessary? I have been letting the tank cycle for roughly 3 months with virtually no water changes but plan to gradually start dosing and injecting CO2 and doing large routine water changes. What, if anything, should I be doing to the tap water I am going to introduce to my tank via water maintain my stable water conditions?
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post #2 of 5 (permalink) Old 12-04-2016, 01:52 AM
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Hi oralsturgeon,

First of all welcome to TPT!

PH and dKH are not especially critical, unless you are running pressurized CO2 in which case I try to maintain a dKH of about 2.0. The more important reading is the dGH, General Hardness, of your water. Dr. Tom Barr, one of the better known planted tank aquarists when it comes to fertilizing recommends approximately a 5.0 dGH for planted tanks to help insure adequate magnesium and calcium for plant growth. I used to use Seachem Equilibrium to increase my dGH which works very well but can become somewhat expensive if you have a large tank or several tanks; now I mix up my own GH booster. Hope this helps!

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post #3 of 5 (permalink) Old 12-04-2016, 02:29 AM Thread Starter
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Thanks. I'll have to get a kit to study dGH. My dual stage regulator is on it's way so I am trying to dial everything in. I would love it if I was able to just directly add my tap water from the tap into the tank but I worry with the pH and kH being so different is this not advisable? or would a certain dGH in the tank buffer this so it won't be a problem. I literally know nothing about dGH. I have kept reef tanks for around 15 years and finally switched to freshwater in the hopes it would be a little less time consuming, cheaper and easier.. not sure that's the case.
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post #4 of 5 (permalink) Old 12-04-2016, 02:52 AM
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What did you use to test the PH? I find it hard to believe that you have an 8.8 PH with a KH of 1.2.

The best way to go is to work with your tap unless you have extreme hard water (300+ TDS). I find it counter productive to modify the tap water. I find it better to understand what is in your tap then adjust the water after it gets in your tank. Usually you'd adjust the calcium/magnesium or GH or even the KH to get the target parameters that you want. KH is typically kept 2 or higher to prevent the PH from getting too low and GH is kept higher than GH by about 3-4 degrees.

Regarding General Hardness, the target hardness can vary but the goal is to ensure that both Calcium and Magnesium is present in the water. Usually getting access to your local water report will give you an idea of how much calcium/magnesium or how much hardness you have. Some cases are known where Mg or Ca is lacking in the water and this is why some would recommend that you dose Ca/Mg from a form of GH Booster to ensure that both these nutrients are in your tank.

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post #5 of 5 (permalink) Old 12-04-2016, 03:42 PM Thread Starter
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I tested my pH using a neptune apex probe recalibrated 3 days ago with the appropriate milwaukee solution and then I cross checked with api freshwater kit. for KH i am using the salifert test kit. According MWRA report. boston water aims for a pH of 9.3 (apparently for purposes of decreasing corrosivity and minimizing leaching of lead and copper) with an alk of 40mg/L. to calculate mg/L into meq/l i get 0.8 meq/L and 2.24 dKH. so the kH in the report is close to where my tank water is whereas the tap water left overnight has a steady kH of about 1.2. Any specific kits you rec for mag and calc? the ones I have left over from my reef tanks are Hanna instruments and are specific for saltwater I believe. Once I get a gH kit I'll test for that. I just worry about doing water changes with tap water directly into the tank when the pH and kH seem so different from the tank water especially since massachusetts has such alkaline water immediately out if the drain.
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