High pH and low KH - The Planted Tank Forum
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post #1 of 24 (permalink) Old 12-19-2004, 04:12 PM Thread Starter
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High pH and low KH

I want to set up my first planted tank utilizing a twenty gallon high, eco-complete, 55 watt AHS kit with GE 9325K bulb, as well as DIY CO2 injection. A sample of water was set aside overnight to test for pH, KH and Gh with Aquarium Pharmaceuticals' Kits. The results were pH: 8.8 (high range test), KH: 53.7 ppm, and GH: 107.4 ppm. Is the KH to low to inject CO2? My understanding is that when CO2 is injected it ultimately affects pH and KH. Any advice on what to do with my water conditions would be greatly appreciated.
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post #2 of 24 (permalink) Old 12-19-2004, 05:36 PM
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I think your Kh is OK, you might want raise it by 1 degree (17.9ppm) with some Baking Soda. I've never used DIY CO2, but CO2 will bring the Ph down. A Ph of 6.7 with a Kh of 4 degrees (71.6ppm) will give you a CO2 content of 22.5 mg/l and that would be OK for a planted tank. Check out some these websites and the sites they lead you too for more info.

www.thekrib.com
www.rexgrigg.com
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post #3 of 24 (permalink) Old 12-19-2004, 07:00 PM
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Your water parameters don't look right. Normally with a kH of 53.7 ppm you would expect the pH to be around 7.6-7.8į. A pH of 8.8 would normally have a kH in the range of 358 ppm.

I would advise you to get the Water Quality Report from your water supplier and try and figure out what they are doing to the water.
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post #4 of 24 (permalink) Old 12-19-2004, 10:40 PM
 
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i have water like that allmost

out of my RO/DI its 8.3 ph with a kh of 5ish ppm i bring the KH to about 90-100 ppm and with co2 i keep the water at 7.4

i have to use RO/DI because my p04 out of the tap is pushing 3ppm i am thinking of adding some peat to lower my ph a little more but i will probly just leave it

on water changes(~25-35 % change) i fill the tank over about 8 hours so there is not a major ph/kh swing and everything stays happy adding Mg, and ca to help with the lowered hardness from the tap
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post #5 of 24 (permalink) Old 12-21-2004, 04:58 PM
 
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I agree with Rex - get a water report because something's definitely whacky.

and Eums...what's wrong with your RO/DI unit? RO water should be 7.0 pH, and almost 0ppm for hardness (which does seem correct)
Carbonate hardness is your alkalinity, so as alkalinity increases so does pH.
Somethings not right.
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post #6 of 24 (permalink) Old 12-22-2004, 04:11 AM
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Newbie question here.

I tested my kh and it reads 15 degrees. How do I find out what the ppm is?

At first I thought 15 was high but after printing the chart on Rex's site I find that with a KH of 15 and a PH of 7.1 my C02 is 35.7ppm just a tad bit low. Right now I am running my Co2 at aprox. 60bpm so I am assuming I need to bump up my Co2.

I know that adding bakeing soda will raise KH. Is there any reason for lowering KH and if so how would you go about doing this.

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post #7 of 24 (permalink) Old 12-22-2004, 04:19 AM
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i dont think his results are wacky. My tap water starts out at 8.5+ with a KH of 1 (GH of 9). After 24 hours it falls to 7.2, and then slowly crashes without any buffering.

I have crushed coral in my Filter that helps out a little, but I still have to add enough Bakins Soda each water change to raise that KH up to 5 or so. I use pressurized co2 so can usually ensure a consistent pH.

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post #8 of 24 (permalink) Old 12-22-2004, 04:21 AM
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Quote:
Originally Posted by Clownknife
Newbie question here.
I know that adding bakeing soda will raise KH. Is there any reason for lowering KH and if so how would you go about doing this.

To lower KH you can either mix with RO water to dilute it (RO has 0 KH). Or you can add Peat Moss to your filter. No idea exactly how much peat to add though. experimentation would be needed to ensure.

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post #9 of 24 (permalink) Old 12-22-2004, 04:25 AM
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Thanks Spar for jogging my memory. I remember reading this in the past. I am going to take water samples tonight and will post them tomarrow.
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post #10 of 24 (permalink) Old 12-22-2004, 04:56 AM
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Clownknife,
I think your at the top of the scale now with the CO2, I don't think you want to bump it up or your going to see your fish at the surface trying to get some oxygen.


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post #11 of 24 (permalink) Old 12-22-2004, 04:13 PM
 
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Spar,
He said he let it rest over night, and still had that high of pH. Therefore, I still say the results are strange.

To convert degrees of hardness to ppm, multiply by 17.9 - 268ppm in your case.
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post #12 of 24 (permalink) Old 12-22-2004, 05:32 PM
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Try a small sample and rest it a full 24 hours. I'm guessing overnight can be something like 8 hours, and my tap water would still be adjusting after that time.
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post #13 of 24 (permalink) Old 12-22-2004, 09:55 PM
 
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drop an airstone in it. that'll outgas the CO2 within 12 hours. But even after 8 hours, if the pH hasn't dropped yet, its fairly safe to say there's not enough CO2 in it to be skewing the true pH when testing.
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post #14 of 24 (permalink) Old 12-23-2004, 02:29 AM
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Quote:
To convert degrees of hardness to ppm, multiply by 17.9 - 268ppm in your case.
Thanks Malkore

I tested the water last night with a Red Sea test kit and this is what I came up with.

KH 13 deg.
PH 7.0 per milwakee controller
GH 3 deg.
Co2 18ppm
FE 0
No2 0
temp=79

I also tested the PH with Red Sea kit both high and low and it read 7.8-8.0. The thing I am confused about is the controller is calibrated at 7.0. What is more accurate the controller or the test kit?

I also want to apologize for the thread hijack.
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post #15 of 24 (permalink) Old 12-23-2004, 03:13 AM
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the controller should be at least +-.1 pH in accuracy (most likely better). testkits have an accuracy of +-.2.

so as long as you have your controller calibrated properly, go with that before your testkit.

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