# Matt: CO2 chart, KH, PH and Carbonate issues



## JRJ (Feb 9, 2005)

Matt,

I was wondering, since starting to use baking soda in your water, if using the KH/PH = CO2 chart was any more accurate for you?

I can't figure out what's happening with my set ups. My KH reads as 4.5 or 5.0 and I drop my PH to 6.1 with CO2. According to the chart my fish should be long dead (+100ppm), but they show no stress. I'm nervous about upping the CO2 because the bubbles are going so fast now that I can't count them.

I used Seachem's Alkaline Buffer for a while because I was getting PH crashes and still noticed no difference in figuring the true CO2 content of my water. I then stopped using the buffer and stopped the crashes by aggitating the surface.

Do you have any ideas?

thanks for any input,

-Russ


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## Rob Tetrazona (Jun 21, 2005)

It was my understanding that the CO2 chart only applies if you do not buffer the KH of your water. Otherwise the chart can be thrown out the window. 

It seems to me like much more than 4 bubbles per second is a waste of CO2, especially if it's coming out so fast that you can't count the bubbles. Your tank will run empty quickly. Somebody was telling me recently how they went thru 10# of CO2 in 3 weeks. 

My settings are around 4 bubbles per second and I can get my pH down to 5.8. Maybe even lower if I tried. I don't keep it there. That was just a test. My KH is 5 and my CO2 level flucuates between 100-120ppm. My fish should be dead, but don't seem to be darting for the water's surface. By that logic, I shouldn't have BBA either, but still do.


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## Bert H (Mar 2, 2004)

I recently posted about this http://www.aquaticplantcentral.com/forumapc/showthread.php?t=10863&highlight=kh+pH here. Bottom line seems to be that it happens to a lot of us, but noone seems to know why/how.


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## JRJ (Feb 9, 2005)

rwoehr said:


> My settings are around 4 bubbles per second and I can get my pH down to 5.8. Maybe even lower if I tried. I don't keep it there. That was just a test.


Sure, just a test. That's just because you have one of them fancy AquaMedic 1000 reactors. :lol:

-Russ


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## MatPat (Mar 22, 2004)

rwoehr said:


> It was my understanding that the CO2 chart only applies if you do not buffer the KH of your water. Otherwise the chart can be thrown out the window.


The pH/KH chart applies only if you are using a carbonate source (Calcium Carbonate or Sodium Bicarbonate) to buffer your water. A lot of those pH down buffers contain a phosphate buffer which alters the pH/KH relationship. Seachem's Alkaline Buffer is supposed to be good for KH since it doesn not contain phosphate buffers.



rwoehr said:


> My settings are around 4 bubbles per second and I can get my pH down to 5.8. Maybe even lower if I tried. I don't keep it there. That was just a test. My KH is 5 and my CO2 level flucuates between 100-120ppm. My fish should be dead, but don't seem to be darting for the water's surface.


I have had my pH down to 5.78 with a KH of 4.5. The fish were fine and the shrimp were not affected by the 200+ppm of CO2 I should have had in the tank. I think it may have something to do with bicarbonates or lack of them in our water supply. I did not keep my CO2 levels that high for very long but maybe I should have.



rwoehr said:


> By that logic, I shouldn't have BBA either, but still do.


Ahh, the plants and algae don't lie  The BBA should be due to low CO2 levels. I still remove a good portion of leave each week when trimming that have BBA on them. I remember Tom saying that if pearling decreases a couple of days after a water change then it indicates low CO2 levels. My tank definately did not pearl as it should have with 200+ ppm of CO2 but it does now by adding the extra Sodium Bicarb???

As for Russ' question, I use Baking Soda to raise my KH by ~2.5 dKH in my 75g. If I only count the bicarbonate portion of KH I add to my tanks, my CO2 levels are in the 60 ppm range. However, I should have a KH in the range of 6.5 - 7 dKH with a pH of 6.1 That should give me 150+ppm of CO2. The total KH can't be correct unless the fish can acclimate to higher levels of CO2 than is expected. I'm thinking it may be possible for them to acclimate to 60ppm but 150ppm is probably not possible.

I am in the same place as you. With a bubble rate that high, it is very hard to make minor adjustments in the rate. I'm not even going to begin to try and count my bubble rate 

I had been using RO water on my 30g tank but between getting sick and the holidays, I let it go a bit too long. I just re-did it earlier in the week so hopefully I can get this KH thing figured out soon. It takes way too long for me to use RO on my 75g!

Do you know any instructors at Wright State who may be able to lend a hand in water chemistry? I have a Comprehensive Water Quality Analysis from the City of Dayton if that would help. Our source water has a total alkalinity of ~270ppm but after it is softened it has 72ppm...


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## JRJ (Feb 9, 2005)

Matt,

Thanks for the reply and for the info on your use of baking soda. Have you tried Seachem Equilibrium with your tap water? Your planned experiment with r/o water sounds interesting - I'd love to know how it goes.

Jason at A&E told me to put some crushed coral in my canister filter when I was getting the PH crashes. I haven't actually tried it since it would be unpredictable and next to impossible to control, but I have thought about using a calcium supplement. Have you tried Plaster of Paris or calcium chloride?

I don't know any chemistry types at WSU, but I'll snoop around a little next quarter.

-Russ


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## J.Sipes (Jul 7, 2004)

I too have had the same experience here,ROb I think it was me that told you about the Co2 tank... I filled my 10lb tank twice in about 2 months running it at god only knows how many BPS... I did a water test and found my PH at 6.2 and I think a KH of 19,any rate whatever the numbers were my CO2 level at one point was 350ppm,My fish should have been dead and BBA or other algeas should be at least in check,I added nothing to buffer the KH or GH for that matter... Both tanks lasted about 3 weeks Tops and I had BBA on almost every crypt and aponogeton crispus and even my Rotala macarandra... GO figure I would do large 50% water changes every week and never once had pearling,nor did the algea fade, I have since given up on that as $30 in 2 months is alot for CO2 and have gone back to about 2 BPS and the BBA has gone away some,the only differnce was the CO2 level obviously changed.. I am going to do a water change and see if I can get the tank back to pearling..

I am confused to why this happens?? Also in the past I used one of the crappy Hagen ladders as my reactor\diffusior and the tank pearled like crazy. I know run the CO2 into a power head through the Venturi port.. I figured with it being chooped or mixed it would be more benifical than the ladder, I am ready to pull the power head and go back to the ladder.
I know my local water supply,which Harrison has their own treatment plant,Told me the Hardness is 250-350PPM on average.
I guess my question is if you get your CO2 level up over 300 PPM,which I had checked at a lab, why would the BBA accure and the fish not be affected?? or no pearling??
Just confused about my CO2 level and BBA.


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## Rob Tetrazona (Jun 21, 2005)

Lenny Llambi wrote all of those "The Stuff that Water's Made Of" articles for GCAS. Maybe he could shed some light on the subject.


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## MatPat (Mar 22, 2004)

I have not found any answers to the KH/pH relationship until maybe today. Rather than bore you with the details, I will give you a link to a post I made earlier today and one I have been involved in for a while. They may hold some answers for us and hopefully some chemist types will add their two cents  I have been curious about the bicarbonate issue for a while now and the first link seems to be an answer, at least in my non-chemist mind 

http://www.aquaticplantcentral.com/forumapc/showthread.php?t=11833

http://www.aquaticplantcentral.com/forumapc/showthread.php?t=10863

For those who are interested in following these threads, you can subscribe to them by using the thread tools pulldown at the top of the thread  Can anyone in the Cinci area find out if Calcium Hydroxide is used for softening purposes? I assume there are several water purification plants in the Cinci area...


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## JRJ (Feb 9, 2005)

The City of Wyoming uses "lime softening" which might be Calcium Hydroxide, as you suggest. I'll try and find out by calling the water plant.

Starting with my next water change, I'm going to experiment with baking soda in one tank and Seachem Alkaline Buffer in the other.
-Russ


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## MatPat (Mar 22, 2004)

Hey Russ, any updates on the Baking Soda and Alkaline Buffer? IS one working better than the other?


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## JRJ (Feb 9, 2005)

I've been in and out so much I haven't really tracked it. I recently started with baking soda, then switched to Alkaline Buffer again. I'm going to switch back to a reactor on both my 75 and 46; I'm using a 5 lb. tank of gas in a couple of weeks with the Azoo diffuser. After the switch I'll try BS (did I say that?) in the 46g and AB in the 75g and do a comparison.

-Russ


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## J.Sipes (Jul 7, 2004)

I finally had a chance to get someone in charge to shed just a little light on my water here in Harrison, she only asked 2 of my many questions.
It seems they buffer the water with Phosphates,no bicarb or carb source, they also stated the water at the treatment plant runs at 7.0-7.2 and when she told them mine comes out the tap at 8.0+ he was confused as to why.. I guess it's time to do some more PH testing here. The only Hardness answer I got was 20GPM. I treid to get a phosphate level and some others but she forgot to ask....They did however state the Iron level was undetected however in some areas it was detected up to .20ppm. I am going to call and see if I can get a complete comprehensive water report, maybe that can shed some light..

I figure the phosphate level had to be high as anytime I dose phosphates I end up with problems. And since they do not use carb or bi-carb, I guess I have no way to figure the CO2 level in my tank....Bummer


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## MatPat (Mar 22, 2004)

John,

I seems that Harrison Twp. doesn't use Calcium hydroxide for water softening purposes, as that should reduce your water hardness somewhat. Calcium Hydroxide also removes a lot of the carbonates/bicarbonates we have in our water supply. Dayton then adds the phosphate buffer (6ppm of P alkalinity in my case) to protect the pipes from corrosion. These two things seem to throw the pH/KH relationship out the window for us.

Post #5 in this link may help shed some light on your CO2 levels. http://www.aquaticplantcentral.com/forumapc/showthread.php?t=11927

Specifically, guiac_boy's below quoted comments are of interest:

"Presently, the thing I'm going by is how much I'm depressing the pH by adding CO2. I take a degassed water sample and compare its pH with the pH in the tank with CO2 running. I'm shooting for a 0.8 to 1.0 pH drop. This should correspond to an actual 30 ppm CO2 concentration."

Once I am 100% sure my tanks KH is made up on only Sodium Bicarbonate, I will run this test and see how it works out. I thnk I am pretty close but want to do a few more Ro water changes to be certain.

Make sure when testing your tap water pH you either aerate it for a while before testing or let it sit out 24hrs before testing. You probably already know to do this, but this will allow any gasses that are under pressure in the supply lines to reach equilibrium with the atmosphere.

My tap pH is 8.51 straight from the tap. The rested tap pH is 7.59. Usually, tap pH tests are lower than the rested since it contains some CO2 under pressure in the supply lines. My higher tap readings seem to be an indication of strange water though I'm not sure just what causes it.

As for your hardness, your water is pretty hard, like you didn't know that  I assume you mean 20 GPG or grains per gallon. To convert GPG to PPM, multiply GPG x 19.12

The dosing of PO4 could cause a problem if you are not adding enough KNO3! Under higher light, I also think plants have a harder time taking up organic NO3 (nitrates from fish waste) than they do the inorganic NO3 (KNO3). Tom talked a bit about this hen he was here but I don't think we ever finished the conversation. Backo on track, PO4 will increase the uptake of NO3 in a tank. I had a very hard time in the past of upping my PO4 levels and keeping my NO3 levels stable. When I would add extra PO4 to my tank, I'm pretty sure the NO3 would bottom out on me, causing algae. I think this may be how the old rumor that PO4 causes algae came to be. I didn't have very good test kits at the time so I really can't confirm this 

There should be some carbonate/bicarbonate hardness in our water but how much of the KH is from carbonate and bicarb sources remains a mystery. It would be nice to have the bicarbonates tested somewhere, but I think the PO4 bufer would still throw off the chart and guiac_boy's idea above may be the best way for us to determine our "actual" tank CO2 levels.


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## Zapins (Jul 28, 2004)

i have found the same thing to be true with my tanks. the water from the tap is 0gh and 0kh. so i used CaCl2 and MgSo4 to raise the GH and baking soda to raise the kh. now my kh is around 9-10 degrees, and the pH is at 6.0 (ph controller). that should put me at 200+ppm of co2 but my shrimp/fish are still alive and i have bba. 

seems like either something universally funky is going on with the co2/bba


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