Advice Needed for Dosing Supplementary ALK

David S

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Randy et al,
For years I've been dosing Kalkwasser to supplement my Alkalinity and Calcium needs, as well as, running it for my top off.
Since the Kalk is not sufficient to supply all the needs of the tank, I supplement with two part.
While this combination has worked well in maintaining my desired levels of ALK & Calcium, I typically have large swings in PH; as much as 0.5, or more, overnight.
I have tried several different dosing schedules of my ALK and Kalk and it helped a little, but not much.
I was wondering, if you or someone with similar experience can offer some suggestions.
My current dosing regimen:
I dose Kalk every 15 minutes, from 7PM to 10 AM.
To supplement, I dose 20 ml of 85% Bicarbonate and 15% Soda Ash - to make the mix PH Neutral.
The majority of the Alk is dosed during evening when I am also dosing the Kalk.
Unfortunately it does not appear to do much for maintaining PH as it continues to plummet.
I know I can increase the Soda Ash in the mix (I have already tried a modest increase with little improvement) but that might raise my ALK to undesired levels).
Anything I can do to optimize my dosing to smooth the PH swings?

BTW FWIW I had a catastrophic event occur to my tank a couple of days ago. I won't go into the details but one of the consequences was a large upswing in Alkalinity.
I discontinued dosing ALK and for last two nights the PH swing is only 0.25.
Coincidence?
 
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blasterman

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Alk has little to do with pH unless its astronomically low. So, decouple alk and pH.

Tank pH dives in the evening as corals and tank biology convert from day metabolic cycle to night. This is normal. My own SPS packed 20L will go from 8.15 to 7.8 daily. Even if I spike the tank with sodium hydroxide during the day and bring it up to 8.3 or 8.4 it will still dive to below 8 at night. I can't add more sodium hydroxide because it adds alk and I'm locked at 10 dKH where I want it.

IMO, dosing alk at night is a waste because stony corals mostly consume it during the light cycle.

Given a choice of where/when to raise pH I would do it during the day starting an hour or two before lights on. Again, stony corals calcify mostly during the day and elevated pH assists calcification. Get your day pH up to 8.3 to 8.4 and if you have some kalk allocation left use that for night.
 
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David S

David S

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Alk has little to do with pH unless its astronomically low. So, decouple alk and pH.

Tank pH dives in the evening as corals and tank biology convert from day metabolic cycle to night. This is normal. My own SPS packed 20L will go from 8.15 to 7.8 daily. Even if I spike the tank with sodium hydroxide during the day and bring it up to 8.3 or 8.4 it will still dive to below 8 at night. I can't add more sodium hydroxide because it adds alk and I'm locked at 10 dKH where I want it.

IMO, dosing alk at night is a waste because stony corals mostly consume it during the light cycle.

Given a choice of where/when to raise pH I would do it during the day starting an hour or two before lights on. Again, stony corals calcify mostly during the day and elevated pH assists calcification. Get your day pH up to 8.3 to 8.4 and if you have some kalk allocation left use that for night.

Thanks for the advice.
Getting PH up is not an issue with me.
Actually, my tank is more likely to have too high PH levels (8.5 or higher).
The problem is it drops like a rock at night (and then skyrockets during the day)
In any event, I will consider changing my regimen and dose my ALK during the day; particularly during the time I am not dosing my ALK.
 

Randy Holmes-Farley

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Thanks for the advice.
Getting PH up is not an issue with me.
Actually, my tank is more likely to have too high PH levels (8.5 or higher).
The problem is it drops like a rock at night (and then skyrockets during the day)
In any event, I will consider changing my regimen and dose my ALK during the day; particularly during the time I am not dosing my ALK.

The low pH at night is from incomplete aeration. Same for the high during the day.

If the daytime high pH is higher than you want, I'd dose baking soda then for alk, not the mix you suggest, although the difference is small.
 
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David S

David S

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The low pH at night is from incomplete aeration. Samne for the high during the day.

If the daytime high pH is higher than you want, I'd dose baking soda then for alk, not the mix you suggest, although the difference is small.
Thanks Randy
So when would be the best time for me to dose the baking soda?
During the day or night? Or during the period I'm dosing the Kalk?
 
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blasterman

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If you have SPS try to dose dose alk / baking soda during lights on. It's when most of it is consumed by hard corals and it does boost growth a bit.

LPS and softies don't care.
 

Randy Holmes-Farley

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Thanks Randy
So when would be the best time for me to dose the baking soda?
During the day or night? Or during the period I'm dosing the Kalk?

I'd dose it during the day when more alk is consumed.
 

Randy Holmes-Farley

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Use Alkalin8.3-P. I use it for ALK and it helps raise PH. Never had an issue with it.

It may be a fine product (most such alk products are just a mix of bicarbonate and carbonate), but there is nothing special about it. If you want a pH boost there are better choices with a larger boost (carbonate or hydroxide), and if you want a pH drop, there are also better choices (bicarboante).
 
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So are you trying to supplement Ca/Alk or stabilize your pH?

As @Randy Holmes-Farley has suggested, Alk dosing can help raise or lower pH. However, I would not suggest unbalanced dosing.

In my tank, I've started to experience daytime pH highs due to my maturing photosynthetic organisms. I addressed my natural low pH of 7.8ish with a combination of Kalkwassr and an oversized skimmer with recirculating CO2 scrubber. As I've also reached the evaporation limit of Kalkwasser to supplement the tank, I've been dosing AFR and 3-part.

My pH-stability solution for my 400L tank consists of Kalkwasser, an oversized skimmer, and a CO2 Scrubber.

I use a doser to continuously drip 2.5ml/min of Kalkwasser. I found the drip to provide a nice consistent pH bump.

I use the skimmer for aeration. It is only automated to come on when the pH needs to be pushed up or down. I use a motorized ball valve to switch between my high CO2 air which will lower my pH and my CO2 scrubber which will raise pH. This allows me to dial in my pH to +/- 0.025. So my tank with an 8.31 pH setpoint typically stays between 8.28 and 8.34.

Capture.PNG


You could probably achieve something similar with Alk dosing and a good reverse lighting schedule refugium. However, I'm not sure you would find "dialed-in" pH stability. I would expect you to achieve higher night pH and lower daytime pH.
 
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David S

David S

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I'd dose it during the day when more alk is consumed.
Thanks again
So are you trying to supplement Ca/Alk or stabilize your pH?

As @Randy Holmes-Farley has suggested, Alk dosing can help raise or lower pH. However, I would not suggest unbalanced dosing.

In my tank, I've started to experience daytime pH highs due to my maturing photosynthetic organisms. I addressed my natural low pH of 7.8ish with a combination of Kalkwassr and an oversized skimmer with recirculating CO2 scrubber. As I've also reached the evaporation limit of Kalkwasser to supplement the tank, I've been dosing AFR and 3-part.

My pH-stability solution for my 400L tank consists of Kalkwasser, an oversized skimmer, and a CO2 Scrubber.

I use a doser to continuously drip 2.5ml/min of Kalkwasser. I found the drip to provide a nice consistent pH bump.

I use the skimmer for aeration. It is only automated to come on when the pH needs to be pushed up or down. I use a motorized ball valve to switch between my high CO2 air which will lower my pH and my CO2 scrubber which will raise pH. This allows me to dial in my pH to +/- 0.025. So my tank with an 8.31 pH setpoint typically stays between 8.28 and 8.34.

Capture.PNG


You could probably achieve something similar with Alk dosing and a good reverse lighting schedule refugium. However, I'm not sure you would find "dialed-in" pH stability. I would expect you to achieve higher night pH and lower daytime pH.
Thanks for the advice.
Impressed with how you limited your PH variation.
Personally, I'd be satisfied with a 0.2 - 0.3 daily fluctuation.
Of note, I do run a reverse lighting system. It was hoped it might reduce PO4 and smooth out the PH fluctuations.
It did work in reducing Phosphate, but I've seen no improvement in PH variation
 

arking_mark

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Thanks again

Thanks for the advice.
Impressed with how you limited your PH variation.
Personally, I'd be satisfied with a 0.2 - 0.3 daily fluctuation.
Of note, I do run a reverse lighting system. It was hoped it might reduce PO4 and smooth out the PH fluctuations.
It did work in reducing Phosphate, but I've seen no improvement in PH variation

I couldn't get my refugium fully operational. My tank seems to want to run ULN and not grow macro algae. :(
 

BanjoBandito

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It may be a fine product (most such alk products are just a mix of bicarbonate and carbonate), but there is nothing special about it. If you want a pH boost there are better choices with a larger boost (carbonate or hydroxide), and if you want a pH drop, there are also better choices (bicarboante).
Breezed through the thread and missed the desired "PH DROP"....certainly not gonna disagree with Randy.
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Dkeller_nc

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Randy noted that the cause of the pH swings in a reef tank between night and day is incomplete aeration. That's correct, of course, but I thought I'd add a bit to his note.

Any seawater system (or any carbonate buffer system) that is in equilibrium with the atmosphere above it will have a particular pH that's dependent on the partial pressure of carbon dioxide in that atmosphere. As the partial pressure of CO2 goes up, either by increased pressure of the total atmospheric pressure or an increase in the percent CO2 in the atmosphere, the pH of the seawater will decrease. That's at equilibrium.

In our tanks, we are rarely at equilibrium with the atmosphere surrounding the tank. Since during the daylight hours the coral, algae and other photosynthesizing organisms are in effect removing the CO2 from the water as part of conversion of inorganic carbon to organic compounds, and the tank water cannot absorb CO2 from the atmosphere at the same rate that the consumers are removing it, the pH rises. During the night those same consumers give off carbon dioxide, and since the tank water can't give off that CO2 at the same rate that it's being produced, the pH falls.

There is another complicating factor to this dynamic, and that's the partial pressure of the CO2 in the atmosphere above the tank. If the tank were outdoors, that partial pressure would be nearly constant (neglecting the small effect of total atmospheric pressure that would change slightly with weather fronts). But indoors, it isn't. For a lot of us, the house is nearly vacant during the daylight hours as we're away at work. So the house CO2 concentration will generally fall to approach the outdoor value. In the evening and overnight, the house is occupied, and the CO2 concentration in the air is generally higher, and in some cases a whole lot higher, than outdoors. This effect of occupied/unoccupied hours has the consequence of exacerbating the daylight/night photosynthesis effect in the tank.

So to the OP, I've a suggestion. You might want to act on Randy's note by running an experiment, which is to add an airpump and a couple of limewood airstones to your tank. Then record/observe the pH swings from before you added them to afterwards. You wouldn't want to leave the airstones in your tank permanently because of salt creep and unsightly bubbles, but if done carefully this experiment will tell you something. You might find out that your pH swings from day/night are considerably suppressed; that might indicate a need to switch to a larger skimmer, or perhaps run an auxiliary one. On the other hand, if you determine that the additional aeration didn't have much effect, then you might reasonably conclude that it's time to add an outside air source to your skimmer intake and/or install a CO2 scrubber on the skimmer's air intake.
 
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David S

David S

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Randy noted that the cause of the pH swings in a reef tank between night and day is incomplete aeration. That's correct, of course, but I thought I'd add a bit to his note.

Any seawater system (or any carbonate buffer system) that is in equilibrium with the atmosphere above it will have a particular pH that's dependent on the partial pressure of carbon dioxide in that atmosphere. As the partial pressure of CO2 goes up, either by increased pressure of the total atmospheric pressure or an increase in the percent CO2 in the atmosphere, the pH of the seawater will decrease. That's at equilibrium.

In our tanks, we are rarely at equilibrium with the atmosphere surrounding the tank. Since during the daylight hours the coral, algae and other photosynthesizing organisms are in effect removing the CO2 from the water as part of conversion of inorganic carbon to organic compounds, and the tank water cannot absorb CO2 from the atmosphere at the same rate that the consumers are removing it, the pH rises. During the night those same consumers give off carbon dioxide, and since the tank water can't give off that CO2 at the same rate that it's being produced, the pH falls.

There is another complicating factor to this dynamic, and that's the partial pressure of the CO2 in the atmosphere above the tank. If the tank were outdoors, that partial pressure would be nearly constant (neglecting the small effect of total atmospheric pressure that would change slightly with weather fronts). But indoors, it isn't. For a lot of us, the house is nearly vacant during the daylight hours as we're away at work. So the house CO2 concentration will generally fall to approach the outdoor value. In the evening and overnight, the house is occupied, and the CO2 concentration in the air is generally higher, and in some cases a whole lot higher, than outdoors. This effect of occupied/unoccupied hours has the consequence of exacerbating the daylight/night photosynthesis effect in the tank.

So to the OP, I've a suggestion. You might want to act on Randy's note by running an experiment, which is to add an airpump and a couple of limewood airstones to your tank. Then record/observe the pH swings from before you added them to afterwards. You wouldn't want to leave the airstones in your tank permanently because of salt creep and unsightly bubbles, but if done carefully this experiment will tell you something. You might find out that your pH swings from day/night are considerably suppressed; that might indicate a need to switch to a larger skimmer, or perhaps run an auxiliary one. On the other hand, if you determine that the additional aeration didn't have much effect, then you might reasonably conclude that it's time to add an outside air source to your skimmer intake and/or install a CO2 scrubber on the skimmer's air intake.
Thanks for the advice.
Actually, I've tried running an air pump at night with virtually no success.
Also grew Macroalgae at night and even when it was growing like gangbusters there was no real improvement in the PH fluctuation.
 
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David S

David S

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I'd dose it during the day when more alk is consumed.
Randy, here's an update:
I've been dosing Sodium Bicarbonate during the daytime.
I've seen no improvement in PH fluctuation.
Last night for example, my PH peaked at 7:20 PM when it reached 8.37 and bottomed at 10:20 AM when it reached 7.83.
This fluctuation is on the "high" side; even for my tank.
Is protein skimming a factor?
Also never bothered to ask; but what might be considered excessive fluctuation?
Would the fluctuations in my tank, eventually be detrimental to the fish and corals in my tank?
Thanks
 

Randy Holmes-Farley

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There's quite little data on the relative merits of pH stability vs a swing. Since your entire range is within the range that folks seems to keep fine reef tanks, I'm not sure I'd worry too much if things you tried are not seemingly useful. :)
 
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