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Ben

KH, GH and pH all over the place

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Hi all,

I have 3 x KH test kits, 2 x GH test kits, 1 x pH test kit and 1 x DSE digital pH tester.

I have measured the pH, KH and GH in my bank of 2 x 6x2x2’s on a 4x18x18 sump. Below are the results.

Sera KH test kit measured 30dKH or 537ppm

Hagen KH test kit measured 350ppm or 19.6dKH

Aquarium Pharmaceuticals KH test kit measured 42dKH or 751.8ppm

Hagen GH test kit measured 140ppm or 7.84dKH

Aquarium Pharmaceuticals GH test kit measured 7dGH or 125.3ppm

Aquarium Pharmaceuticals pH test kit measured a pH of 8.4 (Test kits Max = 8.8)

DSE digital pH tester measured a pH of 8.42

So taking an average my tanks KH = 30.5dKh or 543.86ppm GH = 7.42dKH or 132.3ppm and pH = 8.42

I found a great site to do the conversions from dKH to ppm or ppm to dKH. Site is http://www.hagen.com/usa/aquatic/gh_kh_conv_cal.cfm

So my question is how come my KH value is so high and my pH is still only 8.4?

Why do you think there is such a difference in the KH test kits? I can under stand the difference in the Sera test kit and the Hagen test kit (could be the slight difference in 5ml of water to be tested) but not the 42dkh reading by the Aquarium Pharmaceuticals test kit.

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How old are the test kits as they have a limited shelf life. Also sometimes it could be something else in the tank making the readings go hay wire.

Also with the PH meters have they been calibrated. Also you should never put them in the aquarium you get a clean glass fill it with aquarium water and then put the PH meter in that.

Edited by Nigel

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How old are the test kits

The Sera test kit is about 18 month old. The Hagen about 5years and the Aquarium Pharmaceuticals a few months. I was thinking it could be the age of them but the youngest one is the one giving the strangest results.

Also with the PH meters have they been calibrated.

The digital pH meter was calibrated before I used it.

Also you should never put them in the aquarium you get a clean glass fill it with aquarium water and then put the PH meter in that.

I didn't know that. Nothing about it on the paperwork that came with it either. Thanks for the heads up.

I am going to take a sample of water to a LFS that does testing. I will let you know what they say as a matter of interest.

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I suspect that most of these hardness test kits are lucky to be within 20% of the "true" result.

The kH tests do seem to be particularly disparate though.

pH of 8.4. What did you expect it to be?

Cheers

Brett

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How old are the test kits

The Sera test kit is about 18 month old. The Hagen about 5years and the Aquarium Pharmaceuticals a few months. I was thinking it could be the age of them but the youngest one is the one giving the strangest results.

Also with the PH meters have they been calibrated.

The digital pH meter was calibrated before I used it.

Also you should never put them in the aquarium you get a clean glass fill it with aquarium water and then put the PH meter in that.

I didn't know that. Nothing about it on the paperwork that came with it either. Thanks for the heads up.

I am going to take a sample of water to a LFS that does testing. I will let you know what they say as a matter of interest.

Most of the test kits are to old Ben and I have my doubts about the PH meter. So it will be interesting what the LFS testing shows.

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pH of 8.4. What did you expect it to be?

I would have thought with it still being on 8.4 that a KH of about 12 - 15 dKH. A pH of 9.2 should return a reading of around 18dKH I believe.

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I am going to take a sample of water to a LFS that does testing. I will let you know what they say as a matter of interest.

Ok I went to the LFS today will a bottle of tank water. Here are their findings.

pH 8.8

KH 230ppm or 13dKH

GH 160ppm or 9dGH

Needless to say I bought some new test kits. rolleyes.gif

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Well Ben there you go everything is just what it should be. The only thing the KH is a bit low maybe bring it up to about 280ppm or 16 dkh.

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Yer thanks Nigel. I just gave the bank a hit with Seachem salt and Tang buffer. Will give it a few hrs and measure again. Should be spot on then. thumbup.gif

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Ben,

Kh alone will not boost your pH higher

As Kh is just carbonate hardness, you could add as much bicarb as you want, half fill the tank with it, the pH will not rise above about 8.2-8.4, in fact it could just result in a pH crash if the temp gets too high....!

other carbonates will get it a tad higher but not up to the 9+, hydroxide salts, and other alkalying agents are needed

this is why the tang buffers work better trthan bicarb and calcium carbonate alone

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Seachem tang buffer maintaines a PH of 9.2 to 9.4

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this is why the tang buffers work better trthan bicarb and calcium carbonate alone

Hi Mick,

I only add Seachem Tang Buffer and Seachem Salt to my tanks.

Hi Jim,

Mine isn't there yet. Getting close. 8.8 last measure. thumb.gif

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I have never worried about the PH if the KH is up about 15-18 dKH and you have pleanty of oxygen in the tank then the PH is not importent as it will be up around 8.9-9.0.

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Its just quicker to measure the pH apposed to the KH... LOL.gif

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I just measured the KH and GH again with my new test kits. My KH measured 300ppm thumb.gif . My GH, however, measured 600ppm. dntknw.gif

Could it really be this high? dntknw.gif

I will measure my tap water in the morning and let you know. I can only imagin it is high.

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Ok, I just measured my tap water. KH = 10ppm and GH = 60ppm. cryblow.gif

Any idea's. confused.gif

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What is the substate in the tank and what sort of rocks if any?

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Currently there a 2 x 6x2x2's on the system. Both have size 2 coral sand substrate.

I am about to put a 3rd tank on the bank, a 6x2x18. I will have coral substrate also.

The rocks in the tanks are fake loges etc, I would presume they have no adverse affects on the buffering of the tanks as they are made for fish tanks.

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Currently there a 2 x 6x2x2's on the system. Both have size 2 coral sand substrate.

I am about to put a 3rd tank on the bank, a 6x2x18. I will have coral substrate also.

The rocks in the tanks are fake loges etc.

There is the problem Ben you have to take out the Coral Sand and then the GH will stabilize. I tried tell every one before you cant have a reactive substrate and use these buffers and cichlid lake salts.

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