# pH refuses to drop despite CO2 addition....



## Overfloater (Apr 2, 2004)

This problem has been baffling me for about a month now. I have been pumping quite a bit of CO2 into my tank and my pH refuses to drop below 7.6. 

About a month ago I noticed some BBA starting to pop up. No problem CO2 is probably low. I checked pH and it was 7.6 despite being 6.6 for the last several months. I have essentially no surface agitation so I don't think I could be losing it there. I tried to rectify the situation in the folowing ways:

1) I built a new reactor of smaller diameter to increase velocity and hopefully dissolve more CO2. No help.

2) I upgraded my filter form a Fluval 204 to an XP3. Despite the huge increase in water flow through my reactor, no help. I opened my needle valve way further than it should be and that didn't help either. I can hear the bubbles going into the reactor and none come out of the spraybar. 

3) I bought a new pH test kit because my old one may have been bad. It reads the same as my old one. 

I used a compressed setup and my kH is 8 as it has always been. I bubbled CO2 directly into the pH test tube and it dropped the pH to 6.0 (yellow) in about 5 seconds, so the kit is obviously working. I can't figure it out. I'm open to ideas.


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## Bert H (Mar 2, 2004)

That's a tough one.  Bob, why don't you try an in-tank reactor and see if that drops your pH. You will be able to verify that gas is indeed getting into the tank, and if that drops your pH, then your problem lies somewhere in the gas line. If you see the gas going in the tank and the reactor is dissolving the bubbles, but your pH still doesn't drop, then some of our 'chemists' need to chime in.


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## RTR (Oct 28, 2005)

Or perhaps an issue with surface disturbance? Input rate means little if the CO2 is being off-gassed faster than the input.


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## anonapersona (Mar 11, 2004)

*or leaks*

Or, you are putting gas into the reactor but it is leaking out. Check all connections.


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## Jason Baliban (Feb 21, 2005)

Did this start after a CO2 canister change?

jB


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## Overfloater (Apr 2, 2004)

Jason Baliban said:


> Did this start after a CO2 canister change?
> 
> jB


I believe so. But I'm not 100% on that. Your theory??

Thanks for the quick responses. I have triple check all connections. I can't find any leaks. I have essentially zero surface disturbance. Less than I had when I could hit 6.6 no problem. I may have to grab an in-tank diffuser such as the Boyu to test that theory.

The weirdest part is that I had been running the same reactor and filter setup for several months with no problems hitting my target pH. Perhaps something besides kH has changed in my water... but I have no idea what could have this kind of impact.


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## SnyperP (Dec 10, 2004)

My guess is it's the reactor. Does it sound like it's gurgling water? My old reactor had this problem because the diameter was too small. It built up a gas bubble quickly and co2 would stop dissolving efficently into the water. Turning up the co2 just made the problem worse. Since you're using a canister to power you're filter, i don't see how a venturi loop can be added. 

I solved my troubles by switching out to ceramic diffuser.


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## Jason Baliban (Feb 21, 2005)

Maybe its not CO2? 

If you see bubbles in your reactor, then you would think there has to be some type of gas in there.

How bout taking a sample of tank water and seperating it from the tank. Wait 24 hours and test PH. See if there is a difference. If there is not much difference then i would think you have a leak in your CO2 lines or the bottle is not CO2. I have never heard of it happening, but I have always had it in my mind...."what if this is really not co2".

jB


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## Overfloater (Apr 2, 2004)

Well if I inject the CO2 directly into my pH test tube it will quickly lower the pH as I mentioned, so it is definitely CO2 in the bottle. 

My old reactor always sounded like it was half full of air... when my pH was 6.6 and now that it is 7.6. The new reactor I built makes no noise however. 

This is totally bizarre. We cannot defeat the laws of science therefore I can only assume I have a problem somewhere that I have not found.


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## Jason Baliban (Feb 21, 2005)

Very interesting indeed.....I did not catch the test tube test for PH.

If you remover your co2 line from the reactor does water come immediately, or is there a good amount of gas first?

jB


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## Overfloater (Apr 2, 2004)

Well if I remove my check valve from the CO2 line, water wants to spary from the line. I removed the check valve and tried to blow air into my reactor while the filter was on and I couldn't even come close to overpowering the water force. I could hear CO2 going into the reactor though, so this may be insignificant.

Regardless I removed the CO2 from my reactor and hooked it to a ceramic airstone that I have placed at the bottom of the tank. When I get home from work in four hours I will check the pH and report back.


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## Jason Baliban (Feb 21, 2005)

Yeah.....keep us informed....this is a mystery.

jB


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## anonapersona (Mar 11, 2004)

A plastic check valve??

I had bad luck with these with DIY CO2, the CO2 corroded it and it leaked.


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## Overfloater (Apr 2, 2004)

Yes it is a plastic check valve. As I have mentioned though, I could hear the CO2 being dispersed into my reactor so I know it was going in.

Well 4 hours later and it hasn't moved a bit.. <GRRRR> I'm at a loss. I'll leave the stone running all night and check it in the morning.


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## anonapersona (Mar 11, 2004)

*hearing, how much?*

Yeah, you may hear CO2 going in, but what if you are losing 75% off it to a leak? I suggest removing the checkvalve, and backing of the input rate, then test carefully to see if pH moves. If I am right and you do not back off the input rate or do not monitor carefully, you could drop pH too fast and stress fish.


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## RTR (Oct 28, 2005)

Fish don't read the pH changes from CO2 addition,as there is no significant TDS change involved, just acidification. These changes are not like phosphate or bicarbonate additions for buffering, which do involve potentially osmotic shock differences in short time frames.

Perhaps the pressure in your reactor/hoses are too great for the operating pressure of the CO2 gas? Is there any simple way of reducing the back pressure on the reactor/hoses (such as removing the spraybar if such is used?)? 

But I would get rid of the flapper valve first.


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## Overfloater (Apr 2, 2004)

I tested the check valve and it is not leaking. 

I had no results from the cermaic stone. After about 8 hours. 

I plumbed the CO2 line into my XP3 intake and let it run about 15 hours. No change. 

Today when I got home I decided to bubble CO2 into a glass of aquarium water for 20 minutes. The pH dropped to 6.0. 

The CO2 is definitely getting into my reactor so I don't think back pressure is a problem.

At this point I hooked my reactor back up too see if maybe I'll get lucky because at this point, I have no idea what is going on. When I get home from work in 6 hours, I'll report back.


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## Laith (Sep 4, 2004)

This is a strange one...

From what you've tried so far, it seems that the CO2 is having an effect in small volumes of water (pH tube and glass of aquarium water) while it does not lower the pH when applied to the volume of water in the tank. I'd imagine that if for some reason the CO2 percentage in the CO2 tank is only about 10% (instead of 99+%) it would have an impact on a small volume of water but not on larger volumes?

Clutching at straws here :-s ...

Just out of curiousity, if you turn the CO2 off completely, does the pH go up any? But at a KH of 8 and a pH of 7.6, you're already down to 6mg/l of CO2 so not sure whether it would make a difference... It'd be interesting to try anyway.


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## anonapersona (Mar 11, 2004)

OK, is the valve on the CO2 tank fully open?
Assuming a Milwaukee regulator, is the regulator knob engaged to keep the correct pressure, something around 10 to 20 psi? Milwaukee says to try to use the main knob not the needle valve for adjustments. 

Wait, you got no results from ceramic stone? Did you observe bubbles coming out of the stone? Or no bubbles?


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## Overfloater (Apr 2, 2004)

Thanks for chiming in guys.

Laith: I suppose your idea is plausible. I'm not sure if my pH rises with the CO2 as my test kit tops out at 7.6. I guess the only way to find out if the bottle is pure CO2 is to replace it and see what happens.

Anona: Yes the main CO2 valve is fully open. I have a JBJ regulator, therefore there are no adjustments except the needle valve. I cermamic airstone was pumping many many tiny bubbles which all nearly dissolved before hitting the surface, yet no change in pH. I used this same airstone in the glass of water and it worked very well. 


The only thing left I can think of is either the bottle is not 100% CO2 as Laith suggested or somehow I am outgassing every bit of CO2 that I put in; which I find extrememly unlikey considering there is virtually no surface disturbance.

Hmm...


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## dennis (Mar 1, 2004)

How positive are you of your kH and pH readings?


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## anonapersona (Mar 11, 2004)

I'd like you to try to run the airstone overnight, I'm wondering if your plants are just taking in the CO2 so fast that it is not accumulating in the tank. Not offgassing, but being used up.


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## Overfloater (Apr 2, 2004)

dennis said:


> How positive are you of your kH and pH readings?


I am 100% on those readings.

The airstone was running all night with no change.

I am going to grab another CO2 tank and give that a shot.

EDIT: The CO2 supply shop assured me that there was no way I could have anything but 100% CO2 in the tank, which is what I had suspected. I swapped out the tank, and we'll see what happens.


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## czado (May 26, 2005)

> Laith: I suppose your idea is plausible. I'm not sure if my pH rises with the CO2 as my test kit tops out at 7.6.


Are the colors of the test strange? When I was curing cement in an aquarium pH soared over my test, but the color gradually came back to the test range. Going by the assumption that pH is well over 7.6 and any drop from CO2 injection does not drop pH below 7.6, have you changed anything in the tank? Checked with the water company to assure there is not some strange buffer? It appears you have ruled out equipment variables, and what is left is water and the tank.

Best of luck to you by the way. I hope you figure this out.


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## AquaticMagic (Aug 9, 2005)

Could you shoot a pic of your reactor and how many bubbles per second do you inject?


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## Overfloater (Apr 2, 2004)

Czado: I haven't seen any weird colors in the test kit. It tops out at a blusih color around 7.6, maybe a bit higher. I have not changed anything in the tank. I haven't called the water company, it is probably a good idea to call them though and see if they know anything. I don't know what buffer could be causing this though. 

AM: I don't think there is much point in shooting a pic of the reactor considering that you won't be able to see the CO2 injection anyway. 

My next procedure is that I am going to bubble the CO2 into about 4 gallons of water for 30 minutes too see how much the pH moves.


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## Overfloater (Apr 2, 2004)

Overfloater said:


> Czado: I haven't seen any weird colors in the test kit. It tops out at a blusih color around 7.6, maybe a bit higher. I have not changed anything in the tank. I haven't called the water company, it is probably a good idea to call them though and see if they know anything. I don't know what buffer could be causing this though.
> 
> AM: I don't think there is much point in shooting a pic of the reactor considering that you won't be able to see the CO2 injection anyway.
> 
> My next procedure is that I am going to bubble the CO2 into about 4 gallons of water for 30 minutes too see how much the pH moves.


Yes success! The 4 gallons went to 6.6 in an hour. I started bubbling a good amount of CO2 through the airstone into the tank last night at 11PM, I just checked the tank and it is down to 6.6. 

I'm not sure what I was missing. I will keep the airstone for awhile and monitor it's progress.


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## Jason Baliban (Feb 21, 2005)

So did the PH go down after you changed co2 tanks?

jB


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## Overfloater (Apr 2, 2004)

Jason Baliban said:


> So did the PH go down after you changed co2 tanks?
> 
> jB


It would appear that way.


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## Jason Baliban (Feb 21, 2005)

Wow....

It just makes you wonder doesnt it? Well at least you are back in business!!!

jB


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## Overfloater (Apr 2, 2004)

Jason Baliban said:


> Wow....
> 
> It just makes you wonder doesnt it? Well at least you are back in business!!!
> 
> jB


Yes it does. Lets get back to growing some weeds


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