Help with pH and kH Chemistry - The Planted Tank Forum
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post #1 of 5 (permalink) Old 09-27-2020, 01:48 PM Thread Starter
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Help with pH and kH Chemistry

Week four of high-tech nano. Tropica soil and mix of low-to-mid/high light plants. Plants are growing well. Algae is growing well too (but totally overwhelming). :-)

Using tap water + Prime. Out of the tap pH is 7.6, kH is 2.

In the tank, kH doesn’t change much, gH hangs around 5 or 6 (I’ve added some booster) but pH drops over a few days to 6 or slightly lower. Water changes bump the pH up to around 7, but then they drop again over a day or so.

Thinking I need to adjust parameters of the tap water to pH around 7 and kH to at least 5?

My understanding is that the Tropica soil will continually work towards lowering both (at least for some time).

Want to make sure I’m getting this right before adding any livestock (in addition to the snails that hitched a ride on the plants).
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post #2 of 5 (permalink) Old 09-27-2020, 01:57 PM
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Hi Ricky,

Question: what do you want the pH to be long term?

Adding KH will quicken the depletion of the buffering capacity of the soil, and will raise the pH. That could be good or bad depending upon what livestock you are intending to add to the tank.
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post #3 of 5 (permalink) Old 09-27-2020, 03:48 PM
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I think you might be misunderstanding the kh/pH relationship?

Kh of 5 will make it very difficult to get to pH of 7.

And you said Hi-Tech? Are you testing pH of fully degassed water? What is your pH drop with co2 look like over the week? Also assuming you are testing pH of tap after it sits for atleast several hours? Some municipalities put chemicals in the water that artificially raise the pH. Not sure if Prime removes those?

Algae growth can be a result of many things but in a new tank it often times is too long of a light period. If you are over 6 hrs, I'd say drop it down for the short term.

My 10 gal tank runs at 1 kh, 6 Gh. Degassed pH runs around 7.1-7.2. Full co2, pH hovers around 6.0. Aquasoil substrate. Light is ramped with only 3 hrs full intensity, 6 hrs total. Tank has been running for over a year.

Shot glass is holding down the Monte Carlo, which has finally decided to pull up from substrate, lol!

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post #4 of 5 (permalink) Old 09-27-2020, 10:36 PM Thread Starter
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Quote:
Originally Posted by en7jos View Post
Hi Ricky,

Question: what do you want the pH to be long term?

Adding KH will quicken the depletion of the buffering capacity of the soil, and will raise the pH. That could be good or bad depending upon what livestock you are intending to add to the tank.
pH closer to 6.8 on average? Livestock-wise, nothing too extravagant: considering a betta, some Pygmy Corys or Otos, maybe some Ember Tetras. Wondering which snails or maybe some Cherry Shrimp.

Quote:
Originally Posted by pauld738 View Post
I think you might be misunderstanding the kh/pH relationship?

Kh of 5 will make it very difficult to get to pH of 7.

And you said Hi-Tech? Are you testing pH of fully degassed water? What is your pH drop with co2 look like over the week? Also assuming you are testing pH of tap after it sits for atleast several hours? Some municipalities put chemicals in the water that artificially raise the pH. Not sure if Prime removes those?

Algae growth can be a result of many things but in a new tank it often times is too long of a light period. If you are over 6 hrs, I'd say drop it down for the short term.

My 10 gal tank runs at 1 kh, 6 Gh. Degassed pH runs around 7.1-7.2. Full co2, pH hovers around 6.0. Aquasoil substrate. Light is ramped with only 3 hrs full intensity, 6 hrs total. Tank has been running for over a year.
Seems like I might be misunderstanding the relationship of pH and kH. Happy to learn more. :-)

I tested de-gassed water about a week ago, but hadn’t started my official log book yet. If I remember pH was still about 6. Will check again at end of CO2 cycle today and pre-CO2 cycle in the morning for comparison.

Just tested days-old tap water: pH still 7.6

Light cycle - likely longer than it needs to be: Fluval Nano “Planted” set, dimmed across the spectrum by about 20%, shortened to 9 total hours but a 50% dip for about two hours in the middle of the day. The original set was about 2 hours longer than that. Will bump it all back even more.

Getting back to pH, understanding that pH drops during the day from CO2 (I get that you’re not supposed to “chase” pH), what I’m missing is: why is it “supposed to” rise again overnight?

I’m concerned that (potentially - will have to measure more frequently) the only time I see pH toward a more “normal” range is with water changes. That was my thinking in adjusting the tap water accordingly to begin with.

Thanks in advance for anyone else’s thoughts and clarification.
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post #5 of 5 (permalink) Old 09-28-2020, 03:13 AM
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Quote:
Originally Posted by RickyMcG View Post
Seems like I might be misunderstanding the relationship of pH and kH. Happy to learn more. :-)
I put a ? at the end because I didn't know if I was missing something from your post. Lol! :-)

Yeah, if you're testing while co2 is on its going to be difficult to get a handle on what is going on. Without also knowing what your pH is fully degassed.

And it can, not always, take some time to fully degas. My 10 gallon takes closer the 48 hrs. But that timeframe depends on surface agitation. My return to the tank gently ripples the surface but I don't have whitecaps, lol.

So I think what is happening is that you are looking at pH values during co2 and it's taking longer than overnight to see your pH come back to normal.

With new Aquasoil I do think your kh measurement is incorrect. But I could be wrong. Do know that kh testing is affected by co2 in the water but it may be slight. That and a tap water pH of 7.6 would indicate a kh higher than 2 dKh. In my experience it would put your kh at 4 or so. But again, I could be wrong with that.

With you seeing pH higher right after a water change, than dropping over time, it makes sense that your Aquasoil is pulling Kh (it does that rather well), which would lower your starting pH.

Hopefully that makes sense? :-)

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