# pH buffers and CO2 levels



## niko (Jan 28, 2004)

I have a tank that has EcoComplete as a substrate. Because of the substrate I can't calculate the CO2 levels using the KH/pH table.

EcoComplete contains pH buffers and I can't get the pH below 7.2 despite the strong CO2 injection. KH is 3. The plants bubble very heavily and grow extremely fast - proving that the CO2 is at a good level.

How exactly a pH buffer affects the CO2 that is usable by the plants? 

Also - is there a way to neutralize a pH buffer?

--Nikolay


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## MatPat (Mar 22, 2004)

Niko,

I never really had much of a problem dropping my CO2 with Eco as a substrate. I use my Magnum as a reactor and after replacing the floss my pH has severly dropped. It used to be pretty stable in the 6.8-7.0 range with a KH of 7. Now it has dropped to 6.5 ! The KH is still at 7 so I have a whopping 66ppm of CO2!

I'm not sure the CO2 concentration is correct since my Blue Rams have spawned this week (but they ate the eggs), none of the fish seem to be gasping and the corys and shrimp are staying put on the bottom. I figured I wouldn't mess with it since it seems to be doing no harm.

I'd be very curious to hear more about the pH buffer in Eco. Did you contact Carib Sea about the buffer?


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## gnatster (Mar 6, 2004)

> EcoComplete contains pH buffers and I can't get the pH below 7.2 despite the strong CO2 injection.


I am guessing you have seen this thread.

How long has the tank been setup with EC as the substrate? For me it has been 4.5 weeks and I am just settling in at 7.1 just before lights on, climbing to 7.4 during the photo-period.

As to the chemistry part of who effects what and when or why I defer to the experts.


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## Sgtreef (Jul 4, 2004)

I have the same problem with my Eco complete in the 125 can't get the ph below 7.5.
the Tahitian moon is no problem have it in another tank and I can drop the ph down on it but not as of yet until I increase the light higher.
So must be one heck of a buffer in it.
My 2 cents


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## dennis (Mar 1, 2004)

Interesting,

At first I had heard about eco's buffering effect and so was woried about being able to check my CO2 levels. My understanding was that the effect wore off in a couple of months. So then I set up a tank with Eco and began to check the kH/Ph and monitor it. THe Eco raised my Kh from it normal 2-3 to 8. My pH sems to stay around 6.6 or so (yup, ~60ppm co2) but I have hit 6.4 on really hot days when the needle valves were not adjusted correctly. The heat seems to increase the tank pressure thus giving me a higher bubblel rate. I feed my CO2 into the input of a Fluval 104 (its a 15 gallon) using a small Lee's plastic airstone (the kind with the replaceable "stone" sleeves)

I have, on this and other CO2 inject tanks, occasionaly played with very high CO2 levels. Just for my own curiosity. I know that much over 30ppm is just waste as the plants don't use it but I was curious. There have been times where I have had CO2 levels in the 90's for a day or two with no fish loss, not really even any distress. Guess my O2 levels were high enough that they were still oK.

I do feel that I am toying wiht disaster when I have done this though so I onluy have tried it under very controled circumstances. I still now try to maintain a CO2 level around 30. The only reason my Eco tank is so high is that I am trying to adjust it slowly. My conditions here seem to lead themselves to algae outbreak in a day if my CO2 falls. I don't want that again. I will slowly bring the levels down to 30 and see what happens. I do wonder how the higher pH will affect a couple of my plants like the Tonina and Eriochalion(spelling?) sp.. 

Just the ramblings of someone not awake enough yet.


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## plantbrain (Jan 23, 2004)

Do what I awlays do, add some peat in the substrate and mulm to counter act the pH buffering, I do the same thing with Onyx which also raised the KH.

I had no issues with pH on the EC tank I had.

After the peat wears off, so does the buffering, typically in 2 months or so till the bacteria settle in and start controlling the redox which trends to buffer to neutral in FW soils. 

Regards, 
Tom Barr


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## gpodio (Feb 4, 2004)

Wouldn't you still be able to measure CO2 by measuring both PH and KH? You just don't have a stable KH but the CO2 relationship should still work right? I mean it's not a phosphate buffer or some other form of buffer that would throw off the CO2 calculation is it? 

Tom, wouldn't the use of peat also throw off the CO2 calculations?

My eco-complete tank is 3 months old now, I do 100% water changes with pure RO/DI and by the end of the week KH has gone from 0 to 3-4. Which is fine for me but I'd like to see it taper off soon as I'd like to keep the KH lower in this tank.

Regards
Giancarlo Podio


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## plantbrain (Jan 23, 2004)

I do not add a lot of peat. I've never had an issue with the CO2. 
If you are using pure RO with 0 KH..............well there's much more reason to dissolve the CO3's out of the gravel.

Dissolution will greatly increase if the gradient is much larger. 
See if the KH rises if you add KH 3 reconstituted water. 

About CO2:
I do not pay much heed to keeping the CO2 at a certain set range based on pH/KH readings if things just don't look right in the tank.

If the CO2 measurement is going to be off...................it's going to have less CO2, not more as a general rule. So I'll add a little bit more incrementally. Until I see the plant growth I know I should have and no signs of fish CO2 stress. 

The approach is similar to finding optimal Traces levels which are difficult to test for. This gets around poor test kits and focuses on the plants themselves. Some kits are just unable to tell you what you need to know. 

Get the rest of the parameters in good ranges, then isolate the variable of 
interest.

As long as you have a way of adding a known steady amount(Rate), you can find the CO2 injection amount you need.

Keep adding more till you no long get a good plant response. 

I suggested 20-30ppm for plants some time ago by doing this. I'm leeary to suggest others try this without a careful eye, good steady delivery of CO2, turn your CO2 off at night(reduces any errors or build up that might occur with a 24/7 routine).

Years later I found a reference by Bowes on photosynthetic characteristics (CO2 and light saturation maximums) that showned 30ppm as the maximum amount that will help plants.

The "off at night routine for CO2" is similar to the notion I use for dosing of the nutrients(Estimative index). 

With the KNO3 etc .....you add a bunch and then do a large water change to remove it all to prevent excess build up. 

But with gases, the off gassing at night provides this prevention of build up of excesses. So no water changes are needed to achieve the same result on a daily basis with gases.

Amano does the same thing. Cranks the CO2 in there, then shuts it off at night. 

Screw the "pH stability is better" idea. I've never found that to have merit and I've been doing this for over a decade with all these so called wimpy fish. 

By isolating the parameter of interest, you get a much better idea of what is going on and how to get around poor testing procedures.

This is what helped me figure many things out were many other folks had problems in the past. 

CO2 is a bit tougher due to high levels causing fish issue but still to this day, I've never killed a fish with CO2 gas.

There's also another way to arrive at a close approximation of CO2 with peat.......but that's another post....

Regards, 
Tom Barr


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## gpodio (Feb 4, 2004)

plantbrain said:


> I do not add a lot of peat. I've never had an issue with the CO2.
> If you are using pure RO with 0 KH..............well there's much more reason to dissolve the CO3's out of the gravel.
> 
> Dissolution will greatly increase if the gradient is much larger.
> See if the KH rises if you add KH 3 reconstituted water.


Good point, I'll have to try that, even though my scope is to have this tank run consistantly on 0-1KH. Hopefully the effect will taper off with time.



> About CO2:
> I do not pay much heed to keeping the CO2 at a certain set range based on pH/KH readings if things just don't look right in the tank.


That's pretty much the same for me too, I don't really test things much anymore unless I see a problem. But the poster was referring to the eco complete actually throwing off the KH/PH chart for measuring CO2 and I'm not sure that this is the case. I know peat can do this and many PH- buffers, I think you had posted a way to calculate that once...



> ... But with gases, the off gassing at night provides this prevention of build up of excesses. So no water changes are needed to achieve the same result on a daily basis with gases.
> 
> Amano does the same thing. Cranks the CO2 in there, then shuts it off at night.
> 
> Screw the "pH stability is better" idea. I've never found that to have merit and I've been doing this for over a decade with all these so called wimpy fish.


We've been here before , I can't say I've ever killed a fish from CO2 either but I've always assumed that what 'everyone' was saying about the importance of PH stability to be true for fish. I'd love to see that myth broken personally, I'm just not game enough to try it in my tank  For sure the regular fluctuations that occur during large water changes have never hurt any of my fish...

I run CO2 24/7 now, have been for several months, I've found that even raising the rate of CO2 into the filter doesn't change much at all, my main tank likes to remain at 20-25ppm CO2 level and that's as high as it will go for me. Like I've suggested in the past, I feel gas exchange is the biggest consumer of CO2 and that is what is likely to be "regulating" this CO2 level in my tank. In my plant only tank, CO2 level has been fluctuating from 20-50ppm, plants don't seem to care, snails are still alive but no fish in there.

Regards
Giancarlo Podio


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## plantbrain (Jan 23, 2004)

I just cannot see how pH stability with CO2 gas is going hurt fish/help them within the ranges we use and the issue of 50-70% weekly or 2x a week water changes with tap waters for Discus really make me wonder. 

The fish love the water changes, they are not sick which is a sign of stress. I have not had a sick fish in close to 20 years. 

So if this is true, why have I never had any issues? 

The reasoning goes back to observations and PO4 issues, if PO4 causes algae, why don't I have any when I add it?

By using a plant you know, the method should work well.
CO2 induced pH changes up to a pH unit do not seem to cause any issues and I would like to hear why, specifically with CO2, the pH variation is bad for fish, plants or critters. 

No one has shown me anything real here as far as CO2 induced pH changes involving CO2 changes from 3-5 to 25-30ppm. 

Regards, 
Tom Barr


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## gpodio (Feb 4, 2004)

So are you suggesting that PH changes due to CO2 level changes may effect fish differently than PH changes caused from a KH change? If so, would it make more sense to say that fish are sensitive to KH changes rather than PH changes? Or do you find both PH and KH changes to be irrelevant to fish? Could it also be an issue of how long such a change occurs for? I mean a PH "swing" from a water change is quite temporary, soon the water will go back to what it was before if chemistry is maintained. But when moving fish from one tank to another for example, the change in water chemistry is permanent, could that be more of an issue than the temporary swing?

Just wondering where the alleged "myth" came from....

Thanks
Giancarlo Podio


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## plantbrain (Jan 23, 2004)

KH can kill fish if you change it rapidly.GH salts(with CO3) can likely cause issues too if you add a bunch at once once. Any buffer based salt. 

I think what many assumed as too much CO2 was low O2/not enough surface turbulance and the the pH drop isssue is something when adding CO2 with no buffer since they have trouble knowing how much they are adding. I've had not much issue with a KH of 1 degree. 

I'm just saying the observations do not match the fears folks have said for so long. I'm trying to see if others have seen otherwise. Personally I find it very difficult to accept that it causes probelms, why is another matter.

That's the next much more difficult part
Blood is CO2/HCO3 based like our own......we are set up to get rid of CO2, so are fish.

There have been a number of studies done on pH changes but I think most involve non CO2 cases and the pH was manipulated by NaOH/HCl or HCO3, or some buffer acid combo, but I doubt they used CO2.
TRhere are plenty of vendors that sell all sorts of stuff and some of them have done test........... I'd hope.

Regards, 
Tom Barr


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## Edward (May 25, 2004)

The KH variation causes more stress on my Lemon Tetras, Bleeding Heart Tetras and Black Neon Tetras then the pH change. 

Lets start with a tank at KH of 1.0 degree.

- Now, I can turn on a slow dripping flow of water at KH of 1.50 degree. The fish clearly don't like it.
- Or, I can turn on a slow dripping flow of water at KH of 0 degree and see the fish having a good time.

This test was done repeatedly several times. The fish don't like KH even at low levels.


About the pH / CO2 issue? I can take a fish from pH of 4.0 and put it in a tank with pH of 6.5 and vice versa with no problem at all. But the pH must be created by CO2.

Edward


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## Jeff Kropp (Apr 25, 2004)

dennis said:


> I have hit 6.4 on really hot days when the needle valves were not adjusted correctly. The heat seems to increase the tank pressure thus giving me a higher bubblel rate.


I think temperature changes that affect bubble rates are changing the aperture size of your needle valve. Temperature and changing tank pressures should have little effect on your regulator's output pressure. My $10 needle valve changes rates significantly as ambient temperatures rise and fall. Fortunately it slows as it cools and speeds up with more heat. This fits my light cycle needs since night time is cooler and needs less CO2 while day time is warmer and needs more.
___
Jeff


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