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Unread 03/16/2017, 09:26 PM   #126
karimwassef
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Ok. That aligns.

My setup is a little different since the tank is in the garage which is sealed (for temperature) and noone spends any time there. The net effect is a measurable decline in CO2 and increase in pH.

Since I'm using pH as an indicator to add Kalk, this means that less Kalk could be used unless the tank has access to fresh air to compensate.

What I find is that opening the garage doors during the day stimulates an increase in Kalk consumption and a very positive response on coral polyp extension (not sure why the second one happens).

This connects the dots on both the photosynthetic and calcification fronts and potentially introduces a few interesting options to accelerate growth even further.

I will be moving and taking this tank down (most likely). I'm trying to understand the basis of the successful growth I'm seeing here before the change so I can replicate it.


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Unread 03/16/2017, 09:27 PM   #127
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so.. has anyone tested Carbonic anhydrase enzymes in a reef?


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Unread 03/16/2017, 10:29 PM   #128
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https://www.hindawi.com/journals/ijce/2013/813931/



https://en.wikibooks.org/wiki/Struct...onic_Anhydrase

Here's a reference I found for the use of CA (Carbonic Anhydrase). Looks like Zinc is the key mineral here... more oysters??

https://www.chem.tamu.edu/rgroup/mar...-Anhydrase.pdf

coincidentally, there just happens to be a lot of research on these topics because of the interest in CO2 sequestration in photosynthesis (into algal biomass) and calcification (for concrete) as mechanisms.


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Unread 03/17/2017, 12:44 AM   #129
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I don't know of any papers on the relevant enzymes, but I'm not a marine biologist, so I'd be a poor source in any case. I agree that a sealed garage might produce some different effects than the typical tank. How high does the pH get?


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Unread 03/17/2017, 01:11 AM   #130
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without kalk additions, it can get just above 8.25. But my concern is not in CO2 limiting driving a high pH. I'm more concerned with it limiting carbonates.

During the day, with full on photosynthesis, the "borrowing" of HCO3- due to the a limiting CO2 could limit calcification... basically, the carbonate alkaliity is not uniform. It can drop during the day.

I add kalkwasser and that compensates, but since it's triggered on pH, the same mechanism depleting CO2 would limit my Kalk drip by keeping pH high.

To compensate for THAT, I have a sinusoidal pH threshold that my Kalk triggers on. So, during the day, it's 8.4 and at night, it's 8.1... During the intermediate times, it's set to 8.2.

I did this without really understanding what was happening but the results were great! I simply turned off kalk for a few days and captured the pH swings that were naturally occurring without any kalk. I then added 0.2 to the naturally occurring pH swings and used that as my varying threshold.

I now think I understand. By setting my pH threshold higher during the day, I was compensating for the limiting of CO2 that was raising pH during the day. And that kept my Alkalinity up.

When I opened the garage door, I allowed more CO2 back in, again raising Alk.


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Unread 03/17/2017, 01:25 AM   #131
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Here's another paper that walks the same systems in nature:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3932737/

In this case, the open air basically eliminates the issue of CO2 limitation. And in that case, photosynthesis actually helps calcification by raising pH and making it easier to corals to create skeletons.

Their conclusion is that carbonate sediment (sand) provide the necessary carbonate alkalinity and the macroalgae provide photosynthesis to raise pH to help calcification.

This could actually support the idea that an ATS and a sand bed both help captive reefs grow... I happen to have both, also - accidental.


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Unread 03/17/2017, 01:38 AM   #132
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This one talks about flow improving calcification
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4202238/

I also saw more growth when I set up my surge for very high flow.

So:

1. High air/water exchange creates opportunity for rapid CO2 absorption.
2. Kalk on a sinusoidal pH threshold injects carbonate to pull in the CO2.
3. Long photoperiod + Large ATS = high photosynthesis raising pH.
4. Sand bed provides an additional carbonate sediment source.
5. High flow surge improves calcification.

Those are the elements that I would need to replicate in my new system - Fresh air, Kalk, light, ATS and flow.

Everything else is offline - GFO, Skimmer, UV, etc...

I might try a few other experiments with my current tank - since this year is going to be the frag out and tear down year -

Collect the data to track alkalinity and CO2.
Maybe try a heavy oyster diet to add Zinc (intent to support carbonate anhydrase?)
Maybe try to inject CO2 like planted aquariums and compensate the pH drop with Kalk. I run an Alk of 8.5, so this might increase it to the 12 or 13 levels... but I'll take it slow.
I have Randy's three parts and can do that too, but I prefer the Kalk.
Maybe change the light, adding a lot more UV.
Maybe allow a much higher temperature... push 85 or 86... to see if the system is resistant to temperature bleaching.

I'm satisfied with the chemistry here. I'll collect data and get back.


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Unread 03/17/2017, 11:48 AM   #133
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pH at 8.4 should be excellent for aiding calcification. That seems like a very good target.


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Unread 03/17/2017, 03:33 PM   #134
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ok.. taking data points and the biggest source of error is the pH sensor. No surprise there, but even a 0.1 pH error can generate an additional 1 dKH error in reading. The CO2 would need to be off by 50 ppm to generate that large of an error.

Having said that though, I think that the data can be used to calibrate the formula.

One question - I'm using Salifert. Does it matter if I take the water sample indoors to run the test? Does it matter if it sits for a few minutes?


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Unread 03/17/2017, 10:30 PM   #135
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It shouldn't matter where you run the test, and letting it sit for a few minutes will be fine.


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Unread 03/19/2017, 01:37 AM   #136
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@karimwassef, can you explain how you monitor and dose kalk using ph controller.


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Unread 03/19/2017, 03:24 AM   #137
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I use an Apex controller. I have two pH probes and I use one of them to trigger my kalk reactor. For example, if pH is < 8.4, I turn on a solenoid to gravity feed RODI water into my kalk reactor and it drips kalk water into my sump. When the pH is greater than 8.4, my Apex turns off the solenoid.


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Unread 03/29/2017, 09:01 PM   #138
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still haven't had enough time to run the tests without interruption, but here is an interesting vid I thought was interesting on the topic.



I am a little confused about the idea that excess CO2 would reduce the CO3 in the water. Isn't HCO3 the natural form at our pH and corals can use it just as they can use CO3?

Are they just saying that the excess CO2 would reduce the pH and it would take time for that to stabilize and return into usable CO3 at the pH needed for calcification?

I also wondered where the Ca and CO3 in real reefs come from and this basically says that the total is in balance and the total consumption by carbonate users is small enough that the dissolving CaCO3 in deeper waters is sufficient to keep an abundant supply of Ca and CO3 for reefs. Is my understanding correct? Obviously, there's no kalk reactor on the reefs, but the deeper waters are basically acting as a constant resupplying system.


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Unread 03/30/2017, 12:32 AM   #139
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Carbon dioxide dissolves to form carbonic acid, which releases an H+ ion, lowering the pH. That H+ could combine with carbonate to form bicarbonate, and raise the pH a bit. Those are the kinds of changes that are happening.

Corals take up carbonate in some form, but the details aren't clear. In any case, calcium carbonate is more soluble at a lower pH, and thus the energy cost to form it should be higher. At least that's my limited understanding.


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Unread 03/30/2017, 12:55 AM   #140
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so is the video accurate?


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Unread 03/30/2017, 05:37 PM   #141
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I haven't watched it. I'll try to make some time later.


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Unread 04/01/2017, 11:54 AM   #142
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Anyone seen the video?

I'm especially curious about the comment that excess CO2 reduces carbonates and that the primary equilibrium mechanism for calcium and carbonates is deeper water pressure dissolving coral skeletons.


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Unread 04/01/2017, 01:20 PM   #143
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The video seems accurate to me.


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Unread 04/07/2017, 10:51 AM   #144
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Ok. At what depth does CaCO3 dissolve?


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Unread 04/07/2017, 12:34 PM   #145
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I'll try to look up the depth vs dissolution rates, but I've been a bit busy lately. It might take a while. Please ping me back if I don't answer in a few days.


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Unread 04/07/2017, 12:51 PM   #146
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Ok. Anyone else know?


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Unread 04/16/2017, 01:46 AM   #147
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ok. Sorry for the long delay but I needed a long weekend so I can collect enough data to make a conclusion.

First, I'll share the results:

 photo 0_zps1ico3jno.jpg

The bottom chart shows three different test kit results over time. API1 and API2 are both API Alkalinity but one is over a year old (API1) and one is brand new (API2). The Salifert is also a year old, but I thought it would be more accurate, so I used it too.

The orange markers are the calculated result as a function of the measured parameters: pH, temperature, salinity and CO2 ppm.

I was unhappy with the range of measured test results and I could have just shown the new API that lines up best with the calculated result, but in the interest of sharing everything so that we can all benefit, I'm putting it all out there.

The top graph shows the measured CO2 (ppm) level and the measured pH (black dotted line).

I'll get to the yellow dots (back calculated pH) in a minute.

So - the new API comes closest to the expected calculated result. I looked at the error in the input variables to the formula, but none (except for pH) were significant enough to explain the large gaps in the evening (9pm and 11pm). The gaps were very large (1.4 - 1.6dKH) but really constrained in time to the late evening.

I believe I have an explanation... my pH probe is in my sump downstream from my kalk drip (that is in the first chamber from the overflow. This means that during periods of high kalk dosing, the pH probes are reading the "future" pH of the tank, and not the present. When I take a sample for Alkalinity testing; however, I take it from the DT in the center. This means that during high dosing times, my pH is not uniform and neither is my Alkalinity.

My doser kicks into a higher pH threshold in the evenings (needing to push to a pH of 8.3) and that coincides with the large error during that time.

I went back and calculated what the pH would need to have been so the formula would have correctly predicted the measured Alk_API2 result. That's the plotted yellow markers in the top graph.

So - this shows that the formula is significantly sensitive to pH measurement error. All other variables are relatively small in impact. At the largest error, the pH is only off my 0.05! but drives an error of ~1.5dKH...

My conclusions:

1. I need to rerun the test with my pH probe in the same region as I take samples for the Alk test.
2. The high quality pH probe needs to be calibrated frequently to be effective.
3. It should be possible to calibrate the error out. In my case, the error was actually very small except for a couple of datapoints explained above.

I would like to invite others to replicate (please) and post your results too?

Open to all feedback, even and especially the negative stuff but I would like it to be constructive please?


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Unread 04/16/2017, 01:54 AM   #148
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On a different and sad note... I had the unfortunate experience of the CO2 in my garage rising to 900ppm... this has never happened before to this tank since I have always fed my tank outside air which maintained a constant and level CO2 input...

I took it down and hadn't gotten around to putting the new injected in place, when this event happened.

Based on the formula and the timing of the event, this pushed my Alkalinity above 15... and my Acropora almost completely died overnight (most of my SPS were hit hard too). I can't help but wish I had put an alarm system in place or at least fixed the injector sooner. A simple catch would have been to disengage the doser if CO2 goes above 500... the harm of less Alk is much easier to fix than too much.

I realize that most people don't use pH to dose, so this wouldn't normally cause a crash, but in my case it was catastrophic. I share this so that others can benefit from my failure.

I'm still grieving so I haven't uploaded the images yet, but I will, in time.


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Unread 04/16/2017, 02:01 AM   #149
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I guess saying it was cathartic..

 photo IMG_0054_zpsod6rb9rm.jpg

 photo IMG_0058_zpsd04zxvyc.jpg

 photo IMG_0057_zpsqbrehtzm.jpg

 photo IMG_0056_zps8nloxhin.jpg

 photo IMG_0055_zpsrznjv7ux.jpg

ok.. fixing it.


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Unread 04/16/2017, 03:23 PM   #150
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I hope your corals recover well! I'm not sure what to add.

I did check on the calcium carbonate solubility question. Solubility begins about 2 km deep, and increased to about 4 km. Not of interest in our systems. Aragonite dissolves more easily than calcite, so it goes first.


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