rising ph - The Planted Tank Forum
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post #1 of 5 (permalink) Old 06-30-2015, 11:50 PM Thread Starter
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rising ph

I've got a tank with the "rising pH". Here is the current parameters:

* low light tank of moss, bare bottom lots of driftwood, peat and indian almond leaves
* 0 nitrate, nitrite, ammonia
* 80 TDS
* 2 KH
* 10-12 GH (API kit wasnt that clear)
* 3-4 hrs of minimal CO2 injection a day to lower pH

about 2 weeks ago the same 3-4 of CO2 can lower the pH to 6.6; when CO2 is off, pH rises all the way to 7.4

over time, the maximum i can lower the pH is 7.0 [this is with even increased 12 hrs of CO2 injection]. when CO2 is off, pH rises all the way to 7.5 and 7.6

there has been no water change during this period. currently there are CRS residents in the tank.

what is going on over time?
the plan will be to slowly replace the water with RO water. another question is - what is the best way of doing so while adding buffer of salty shrimp mineral? so far the strategy has been to put pure RO water to bring down the TDS.
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post #2 of 5 (permalink) Old 07-01-2015, 12:22 AM
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I think you are still within the error range of hobby level test kits.

Are you using a calibrated pH probe?

Is the KH staying the same?

What are all the ingredients in the shrimp mineral?
Are you adding any fertilizers?

You might try setting up separate 'tanks' (ie. jars like 1 quart canning jars) and trying each additive separately.
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post #3 of 5 (permalink) Old 07-01-2015, 12:25 AM Thread Starter
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I am using a calibrated ph controller. I am sure kh and gh measurements are not accurate. I still havent used any remineralization as I'm trying to lower everything right now

Tomorrow I will post another set of gh kh reading
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post #4 of 5 (permalink) Old 07-01-2015, 01:00 AM
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I would expect your GH to be closer to 4dgh or even less with a tds reading of 80 ppm. Tds translates to roughly 17ppm per degree but that is assuming you only have the minerals dissolved in the water. In your tank there are many other things that get dissolved such as waste from the livestock, leaching from organic materials like driftwood and rocks as well as food and chemicals like fertilizers or chlorine removing treatments.

If you have any rocks or decorations in the tank one of them may be raising the ph. As Dianna has mentioned, your testing method may have an error. In reading your post it sounds like you are relying on your ph controller to give you your ph readings so perhaps the probe is giving faulty readings. If you tell us in detail how you test we may be able to spot the issue. I have never had much luck with the API GH test. I have seen pictures of other peoples test tubes with dramatic color changes but mine are never distinct. Some buffer or other that interferes with the reagents I suppose.
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post #5 of 5 (permalink) Old 07-01-2015, 01:10 AM Thread Starter
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again, no decorations, rocks of any kind in the bare bottom tank - just plants (mostly moss), lots of driftwood, a filter full of peat (soaked, no running water over it).

i definitely question my API gh/kh test - especially the gh. i will test again tomorrow. both i followed instructions to the best of my ability. the KH i tested twice and was 2 drops with a margin of error of 1 drop [i performed it twice]. the GH i only performed once and after it exceeded 10 drops without changing color i was concerned. at 12 it may have changed a little.

my ph controller is accurate as i tested various substance and they were very close within .1 or .2 of the true pH. i dont doubt the pH controller.

my TDS reader is questionable - as its electronic and i dont have any baseline test for it. i guess i have to trust it.

i agree with your assessment and my number one suspicion is my GH is probably lower than i claim. HOWEVER that doesnt explain the pH continuously rising. if anything with plants and etc... it should be dropping and staying low with CO2 injection.

again... i started with tap three or four weeks ago and i just added RO. no remineralization just yet although my ultimate goal is get my water to 6.2pH (low 6s) with 0KH and 4GH via salty shrimp. so the first question again is why is my pH climbing. second question is given where i am how do i get to my desired target parameters.

separate jars is a good idea i didnt think of but tedious work - and it doesnt fully replicate the tank esp with my weird rising pH problem. i need to have a plan of action soon as my water change schedule is coming up in a week or two - right now the plan i 20% RO water change when that day comes.

There is no fertilizer, no chlorine removal or any other chemicals added to the tank. Low lights on the tank does not seem to be the cause of the changes. Just as a hint of water parameter... I have a few strands of hornwort in the tank... It's budding a bit but almost white instead of bushy green... I guess it implies the water parameters are 0 nitrate nitrite ammonia
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