CaCl and MgSO dosing increased PH - El Natural - Aquatic Plant Central

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Old 03-20-2020, 04:53 PM   #1 (permalink)
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Default CaCl and MgSO dosing increased PH

I boosted my GH from 2 to 8 this morning using CaCl and MgSO and when I checked PH this evening it was 7.6, having been at 6.6 in the morning. I was surprised by this increase as I was under the impression that this method would not create a boost in PH. What could explain this sudden increase?

Should I be concerned about inducing PH shock in livestock doing this?
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Old 03-20-2020, 11:29 PM   #2 (permalink)
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Default Re: CaCl and MgSO dosing increased PH

pH should be measured at the same time. Natural CO2 production/consumption causes pH fluctuation. In the morning it's lower (higher level of CO2) and the highests pH is in the afternoon (after the main photosynthesis period, with very low CO2). To keep stable pH, you should have KH at around 5dKH (or more).
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Old 03-21-2020, 06:54 AM   #3 (permalink)
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Default Re: CaCl and MgSO dosing increased PH

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Originally Posted by mysiak View Post
pH should be measured at the same time. Natural CO2 production/consumption causes pH fluctuation. In the morning it's lower (higher level of CO2) and the highests pH is in the afternoon (after the main photosynthesis period, with very low CO2). To keep stable pH, you should have KH at around 5dKH (or more).
Thank you for your response!

I measured again this morning and the pH was still 7.6. I think this level is ideal if it remains stable. Interestingly, my kH has increased from 2 to 4 since dosing mag and cal. Would you recommend adding a small amount of baking soda to increase it over 5 as you mentioned?
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Old 03-21-2020, 08:01 AM   #4 (permalink)
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Default Re: CaCl and MgSO dosing increased PH

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Thank you for your response!

I measured again this morning and the pH was still 7.6. I think this level is ideal if it remains stable. Interestingly, my kH has increased from 2 to 4 since dosing mag and cal. Would you recommend adding a small amount of baking soda to increase it over 5 as you mentioned?
It is always best to adapt to whatever pH your tank has, rather than trying to adjust the pH to some "better" value. It is natural for the pH of the water to vary during the day and even day to day, so no harm is done when that happens. The pH is buffered by the presence of carbonate or bicarbonate and CO2. The pH that it is buffered to is a function of the ppm of CO2 and carbonate, so when the CO2 varies, the pH the water is buffered to also changes.
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Old 03-21-2020, 08:58 AM   #5 (permalink)
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Originally Posted by hoppycalif View Post
It is always best to adapt to whatever pH your tank has, rather than trying to adjust the pH to some "better" value. It is natural for the pH of the water to vary during the day and even day to day, so no harm is done when that happens. The pH is buffered by the presence of carbonate or bicarbonate and CO2. The pH that it is buffered to is a function of the ppm of CO2 and carbonate, so when the CO2 varies, the pH the water is buffered to also changes.
Ok so it sounds like the Ph swing wasn’t caused by dosing cal and mag but as a result of varying CO2?
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Old 03-21-2020, 12:20 PM   #6 (permalink)
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Default Re: CaCl and MgSO dosing increased PH

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I measured again this morning and the pH was still 7.6. I think this level is ideal if it remains stable. Interestingly, my kH has increased from 2 to 4 since dosing mag and cal. Would you recommend adding a small amount of baking soda to increase it over 5 as you mentioned?
I don't know why the additions raised the pH, but I would not add baking soda unless the "morning pH" drops drastically and below 6.8. See what effects the added Ca and Mg are before making another major change.

Main thing is that you have raised the GH from 2 to a much more acceptable GH = 8. Your plants now have adequate Ca and Mg for decent growth. If that was your intent, good going!

I would consider adding a little KCl (salt substitute in grocery stores) if you haven't already.

Things to consider. With greater Ca and Mg, you may get better plant growth. The increased CO2 uptake for photosynthesis may increase the pH. The Ca will probably affect bacterial activity as well.

Hopefully, you will see some benefits from the Ca and Mg additions.
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Last edited by dwalstad; 03-21-2020 at 12:21 PM.. Reason: smoothing things
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Old 03-21-2020, 01:28 PM   #7 (permalink)
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Default Re: CaCl and MgSO dosing increased PH

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Originally Posted by dwalstad View Post
I don't know why the additions raised the pH, but I would not add baking soda unless the "morning pH" drops drastically and below 6.8. See what effects the added Ca and Mg are before making another major change.

Main thing is that you have raised the GH from 2 to a much more acceptable GH = 8. Your plants now have adequate Ca and Mg for decent growth. If that was your intent, good going!

I would consider adding a little KCl (salt substitute in grocery stores) if you haven't already.

Things to consider. With greater Ca and Mg, you may get better plant growth. The increased CO2 uptake for photosynthesis may increase the pH. The Ca will probably affect bacterial activity as well.

Hopefully, you will see some benefits from the Ca and Mg additions.
Thanks, Diana!

That was indeed my intent; Asheville's tap water is incredibly soft. As you speculated, I have already observed more bacterial activity, and I'm finally seeing a drop in ammonia and an increase in nitrite. I'll keep an eye on the pH and look in your book for instructions around dosing KCl. I'm hoping my bowl will soon strike balance with improved plant growth!
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Old 03-22-2020, 05:42 AM   #8 (permalink)
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Default Re: CaCl and MgSO dosing increased PH

Good that you are providing some hardwater nutrients (Ca, Mg, K) to your system.

A small pinch of the KCl (solubilized in a little water) for a 3 gal bowl should be enough. [Check ingredients of salt substitute to make sure that it is actually potassium chloride (KCl).]

Calculations: Pinch would be about 100 mg. Half is element K, so it's 50 mg of K. Three gal is about 12 liters. 50 mg K/12 liters =4 mg K/liter.

This is a reasonable addition when you may be starting with none. Range of K in city drinking water is 0-30 mg/l (or ppm) as shown in Table V-5 (p. 85) in my book. It would be hard to overdose this vital nutrient.
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Old 03-22-2020, 05:57 AM   #9 (permalink)
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Originally Posted by dwalstad View Post
Good that you are providing some hardwater nutrients (Ca, Mg, K) to your system.

A small pinch of the KCl (solubilized in a little water) for a 3 gal bowl should be enough. [Check ingredients of salt substitute to make sure that it is actually potassium chloride (KCl).]

Calculations: Pinch would be about 100 mg. Half is element K, so it's 50 mg of K. Three gal is about 12 liters. 50 mg K/12 liters =4 mg K/liter.

This is a reasonable addition when you may be starting with none. Range of K in city drinking water is 0-30 mg/l (or ppm) as shown in Table V-5 (p. 85) in my book. It would be hard to overdose this vital nutrient.
A pinch it is! I imagine of the many strange items being wiped out at grocery stores, salt substitute isn’t one of them.
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Old 03-22-2020, 06:38 AM   #10 (permalink)
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Default Re: CaCl and MgSO dosing increased PH

You can add a small bag of coral or shell (calcium carbonate) to your filter to help with buffering & calcium. Something where you don't have to think to mess with the kH every water change.
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