Chasing pH stability AND alkalinity stability

[Reefinmike]

I’ve fought high CO2 levels and pH below 7.6 for years. I’ve taken every approach to raising pH short of a CO2 scrubber. I feel they’re too volatile, have great potential to nuke the tank and can get expensive. Randy’s recent article about pH vs alkalinity stability sparked my experiment . I started dosing lye(NaOH) a couple months ago with the end goal of reaching stable pH AND bicarbonate alkalinity- just like the ocean. Lye is very corrosive, can burn you and nuke your reef without proper PPE, research and redundancy. I’m NOT suggesting everyone go out and start dosing lye. Use kalkwasser, soda ash or esv B-ionic for higher pH first. I’m wanting to demonstrate how you can toggle between these ph boosters and things with minimal impact( carbocalcium, all4reef, bicarbonate) for ultimate stability. In extreme cases like mine, lye dosing can serve as a CO2 scrubber AND supplement the bicarbonate alkalinity your corals use.

The first 5 weeks were focused on using hydroxide(NaOH and CaOH) for my alkalinity additive chasing only alkalinity stability. Demand became very difficult to keep up with(2.5+dkh/day), pH reached 8.5+ with up to .55 daily swings despite “stable” alk tests. Some corals started showing distress 5 days ago. I presumed the carbonate to bicarbonate ratio was way out of whack. In the name of science, I dumped in a huge 2.5dkh dose of bicarbonate. Corals immediately recovered, alkalinity quickly dropped and stabilized. It was clear the reef needed carbonate additions. Peak demand stripped the reef of CO2 causing the massive pH spikes.

When alk dropped to normal levels I started the final experiment “chasing” alkalinity stability AND pH stability. The Alkatronic tests every 3 hours and hourly forced tests when I’m outside the 9.5-9.9 range. I’m using one dos head for soda ash when pH is above 8.25 and the other with lye when below. My brake_tap VO omits 1/3 of the dose if the Alkatronic sends a 9.8 signal. Brake_hard omits 1/2 the dosing for a 9.9 signal and brake_stop cuts all dosing at 10.0dkh. The goal is to maintain 9.7+/-.2 throughout the day. Toggling between additives is keeping pH high with the smallest swings I’ve ever seen. This is an ongoing experiment and I’m sure I’ll make some minor tweaks. I’ll document the progress here for anyone wanting to follow. I’ll post all the apex code next.

I know just enough about reef chemistry to be dangerous with it. I may be incorrect on certain things and i’d like to hear the experts opinions.

 

[Reefinmike]

I set a flat 300ml for both dos heads spread evenly throughout the day. The alkatronic reports the test data to the closest .1 via bnc. The value wiggles around a bit. For example, a 9.86 test reports as 9.9 varying between 9.89-9.52. If the alkatronic loses power it sends a 7.00 signal until the next test. The alk error vo cuts the dose to half. The pH vo’s toggle between one additive or the other

 

[Dr. Jim]

Very interesting (although I'm not sure if I understood thoroughly your second part).
I don't know if I'm brave enough to play around with NaOH but you gave me an idea. I wonder if it would be worthwhile to use a controller to dose carbonate when the pH is below a set point; and, to dose bicarbonate when the pH is above a certain set point.

 

[Reefinmike]

Very interesting (although I'm not sure if I understood thoroughly your second part).
I don't know if I'm brave enough to play around with NaOH but you gave me an idea. I wonder if it would be worthwhile to use a controller to dose carbonate when the pH is below a set point; and, to dose bicarbonate when the pH is above a certain set point.

The second post was just explaining the programming with a little background on why i chose certain numbers. I didn’t expect most people to understand it .

using pH to toggle between additives like you suggest is absolutely do-able. Better with an automatic alk tester as well but it’s hard to justify the cost. I would NOT dose amounts blindly to maintain a certain pH. I’d dose a set daily amount toggle between the two like you suggest. I know someone that dosed lye as often as needed to maintain 8.30. He spiked his alk to 16 . If you don’t want to buy the latest and greatest equipment I’d suggest a used apex system and brs1.1ml dosers. I’d be happy to help you with programming.

 

[rmurken]

I’ve used NaOH to maintain alkalinity while letting Ca come down. Randy has a recipe for it. As you point out, it requires care—but is by no means a crazy approach if done correctly.

When you say your alkalinity dropped after adding 2.5dkh worth of sodium bicarb, do you mean your pH dropped? That addition would increase your alkalinity (by 2.5dkh, by definition), but at a tank pH of 8.5, it would simultaneously tend to bring your pH down.

 

[Reefinmike]

I’ve used NaOH to maintain alkalinity while letting Ca come down. Randy has a recipe for it. As you point out, it requires care—but is by no means a crazy approach if done correctly.

When you say your alkalinity dropped after adding 2.5dkh worth of sodium bicarb, do you mean your pH dropped? That addition would increase your alkalinity (by 2.5dkh, by definition), but at a tank pH of 8.5, it would simultaneously tend to bring your pH down.

Correct! I worded it a bit off. When I added the 2.5 of bicarb I saw a small pH drop followed by an alkalinity spike read by the alkatronic. Alk values fell quickly over the next with a notable change in pH stability. Days prior, 8.0-8.5 was a normal daily pH swing. Following days had 0.2 pH swings. Alk tests from the alkatronic were much less sporadic thereout.

i’m no chemist but that tells me dosing lye only led to large swings of free hydrogen ions leading to large swings in bicarbonate availability. A hydroxide ion from lye combines with a co2 molecule to create bicarbonate. From there, the imbalance of hydrogen ions(pH) led to a theoretical skewed bicarbonate to carbonate ratio. Corals seemed to agree. Auto alk testing and most kits can’t differentiate between carbonate and bicarbonate but I believe the seachem test can. I haven’t gone that far

 

[rmurken]

I think by skewed bicarb-carbonate ratio, you mean your pH was too high for the corals’ liking? That’s how I would think of it. The bicarb-carb ratio at a given alkalinity is basically a function of pH as I understand it.

 

[Reefinmike]

I think by skewed bicarb-carbonate ratio, you mean your pH was too high for the corals’ liking? That’s how I would think of it. The bicarb-carb ratio at a given alkalinity is basically a function of pH as I understand it.

In laymen’s terms, yes. This is all theoretical but going off of Randy’s recent article- at a higher pH there are fewer hydrogen ions meaning a higher ratio of carbonate(CO3) than bicarbonate(HCO3). There’s a general consensus among the hobby and scientist that coral absorbs bicarbonate, removes a hydrogen ion via photosynthesis to raise pH within it’s tissue and deposit a layer of Calcium Carbonate aka skeleton.

keeping bicarbonate availability stable is likely more important than total alkalinity. Factoring pH stability into overall alkalinity stability could pay off. Anecdotal but my corals seem to agree.

 

[Dr. Jim]

The second post was just explaining the programming with a little background on why i chose certain numbers. I didn’t expect most people to understand it .

using pH to toggle between additives like you suggest is absolutely do-able. Better with an automatic alk tester as well but it’s hard to justify the cost. I would NOT dose amounts blindly to maintain a certain pH. I’d dose a set daily amount toggle between the two like you suggest. I know someone that dosed lye as often as needed to maintain 8.30. He spiked his alk to 16 . If you don’t want to buy the latest and greatest equipment I’d suggest a used apex system and brs1.1ml dosers. I’d be happy to help you with programming.

I have a GHL Controller and the KH Director (which measures Alk as many times per day as you want and then regulates dosing amount). I'm already thinking about tying the KH Director with pH control so the pH control will dictate which buffer to dose (carb. or bicarb.) and the KH Director would determine the dosage. Shouldn't be too difficult.

 

[Reefinmike]

I have a GHL Controller and the KH Director (which measures Alk as many times per day as you want and then regulates dosing amount). I'm already thinking about tying the KH Director with pH control so the pH control will dictate which buffer to dose (carb. or bicarb.) and the KH Director would determine the dosage. Shouldn't be too difficult.

Sounds like you have the hardware to do the exact thing. I’m not familiar with the GHL software and code but I know our testers are very similar. Definitely worth trying out.

i’d love to see @Randy Holmes-Farley work with GHL, Neptune or Focustronic to develop pH AND alkalinity control with matching cal, mag, part c etc.

 

[Reefinmike]

delete

 

[Reefinmike]

The pH swing opened up a good bit recently while alkalinity tightened up. The holiday weekend had ambient co2 swinging quite a bit which was a good test for the system’s weaknesses. I made a couple changes to help. pH_HIGH was lowered from 8.25 to 8.20 & I modified the brakes for a full dose, 3/4 dose, 1/2 dose, 1/4 dose and no dose. 5 tiers of dosing

-A 9.65-9.74 tronic test sends a 9.69-9.72 signal to the apex and allows 100% of the tData dose until the next test in 4 hours

-A 9.75-9.84 tronic test sends a 9.79-9.82 signal to the apex and allows 75% of the tData dose until the next test in 4hrs

-A 9.85-9.94 tronic test sends a 9.89-9.92 signal to the apex and allows 50% of the dose. The next test is in 4 hours under 9.90, 2 hours at 9.90+

-A 9.95-10.04 tronic test sends a 9.99-10.02 signal to the apex and allows 75% of the dose. The next test will be forced in 2 hours.

-A 10.05+ tronic test sends a 10.09+ signal to the apex and stops all dosing until the next forced test in 2hr.

 

[Reefinmike]

It’s been a couple weeks and things have been going really well considering I was lucky to average 8.00pH beforehand. Having my additive toggle point at 8.20 let things spread out last week so i changed it back to 8.25 7 days ago. pH averaged 8.28 with a +/- 0.08 daily swing. Alk averaged 9.75 +/- .2. I think most people would be thrilled with this but I had to take it further. Alkalinity developed a clear trend of dipping during peak lighting, shortly preceding the peak pH spike. The reverse was true as well. Alkalinity spiked shortly before pH bottomed out- just before the lights kicked back on.

I’ve been dependent on my skimmer for years. It pulled outside air to help offgas excess co2 bringing my pH up about .15 from my old low of 7.70. I’ve struggled with low nutrients since then but just couldn’t ever get away from my dependence on it. Now that my pH averages 8.28 I started thinking... the skimmer is pulling a constant 410ppm of co2 from outside. What if I eliminated it that CO2 addition and let my reef absorb only the CO2 from ambient air in my house?

I pulled the skimmer at midnight dec 10th. pH dipped overnight but not as low as normal. To my amazement, pH flatlined over the next 24 hours. No noticeable “daily” peak or dip.

For the experiment’s sake, I made a poor decision at the dec12th mark. Demand presumably increased a bit from the stable pH and my alkalinity went a little lower than normal. I dumped in 0.7 dkh worth of bicarb. Alkalinity spiked as expected however pH absolutely tanked once lights turned off. Looking back it’s obviously due to my lye dose dropping about 60% overnight. I’m expecting pH will settle out over the next 24 hours. I was thinking about adding a daily bicarbonate dose or a “step” in the dosing wizard to handle the alk dip but I believe I found a better way. I created a virtual output to disable my first dosing brake during peak demand. This should help the system anticipate demand better.

 

[Biologic]

How are things going? I think stable ALK/Ca/Mg/pH is the moonshot for 2025. Since I’ve focused on stabilizing pH and ALK as much as possible, I’ve seen significant growth.

 

[Reefinmike]

How are things going? I think stable ALK/Ca/Mg/pH is the moonshot for 2025. Since I’ve focused on stabilizing pH and ALK as much as possible, I’ve seen significant growth.

This thread kinda puttered out so I've been updating more thoroughly here https://www.reef2reef.com/threads/i...-and-dos-for-stable-alkalinity-and-ph.784144/ seems like a better fit being in the control freak section.

The holidays CO2 swing really put the system to the test; if it werent for my cal and soda ash jugs running dry I'd be able to say it's been flawless. there's lots of rambling between @Brett S and I but I feel it's all very helpful and part of the learning process.