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Old 03-12-2007, 04:55 PM   #1
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CO2 effects on fish - pH swings from CO2

So I've asked a couple people, and searched a few forums, but haven't really found an answer to this question.

How does the lowered pH effects of CO2 affect fish inhabitants? And more importantly, the changes in pH that occur in our planted setups.

Especially for those running pressurized CO2 systems that shut off at night, or DIYers that run a bubbler to provide gas exchange and get O2 in at night. either of these methods would cause the pH in the tank to adjust significantly between the photoperiod and the night time when the CO2 is running or not (or a bubbler offgassing the CO2). So you would have a higher pH at night, and a much lower pH during lighting when the CO2 is running.

Since fish need a stable pH for health, how are these affects handled in these situations, or what is the justification for why this does not affect our fish?
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Old 03-12-2007, 05:00 PM   #2
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The PH swings caused by CO2 injection do not matter. It is swings in KH that cause fish problems.

My PH swings from 7.6 to 6 and back 7.6 every 24 hour periiod. The KH however stays at a nice steady 2.

My fish are all active, colorful and seen very healthy.
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Old 03-12-2007, 05:56 PM   #3
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Just a few quick questions to help me, if nobdy else, understand what is going on a bit better. What would be the typical cause of a kH change? Everyone seems to be against DIY Co2 in larger tanks because of pH swings. I assumed that this was due, in part, to stressing the fish. Is it really just frowned upon only because of algae problems caused by pH swings?
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Old 03-12-2007, 05:59 PM   #4
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Rich is correct.

The pH and KH will normally change together. Most people focus on keeping the pH steady since they are more likely to have pH test kit handy and aren't dealing with CO2 injection. Since fish suffer no ill effects as a result of pH swings caused by CO2 injection, it's pretty obvious that it's actually the KH changes that cause the fish problems.
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Old 03-12-2007, 06:38 PM   #5
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So that explains all the hype about steady pH being more important than being in an advertised target zone for fish? Since the kH is what essentially steadies the pH, I think I can understand that. However, there's debate about kH being affected by CO2 injection, so I guess that's a seperate question - sortof. I have not tested my kH since I began injecting with my DIY CO2, maybe I should - mainly out of curiousity.

I understand that there are tons of people injecting CO2 without adverse affects (that they're aware of) to their fish, but I was trying understand the theories behind it.
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Old 03-12-2007, 06:52 PM   #6
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If you are losing your water's buffering ability (kh), that is an enormous problem. The kh is what keeps your ph steady.

What I've read about DIY CO2 injection causing issues is that the CO2 was not being dosed correctly, leading to kh drops and subsequent ph issues.
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Old 03-12-2007, 08:56 PM   #7
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Here are my thoughts on the DIY CO2. When you use DIY it is hard to maintain steady levels. To combat this we try to stay over 30ppm. The problem is that the DIY is variable, you can forget to change a bottle, a mix can fizzle, house temps can drop during the winter or with excessive AC. This causes the CO2 levels to bounce around. The algae can adjust to this the plants can not. You therefore get an excess of algae and poorer plant growth.

As far as I know the fluctuating levels have no effect on KH or the fish. The danger to fish is if the solution in the bottle backs up in to the tank, then you can have a real problem on your hands.
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Old 03-12-2007, 09:01 PM   #8
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I am battling the fluctuating DIY levels right now, and I'm aggrevated like crazy. Hence why I'm currently scouring ebay and craigslist for cheap tanks. haha

But still, even with a system thats under control, with the CO2 going on and off each day via timer or whatever, this is the fluctuation I was referring to in regards to fish health.
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Old 03-12-2007, 09:02 PM   #9
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If you think about salts, such as baking soda which is the common KH buffer, this will explain the fish issues.

CO2 is not a salt.

Baking soda is.

Fish osmoregulate their blood and internal organs.
They exchange CO2 all the time and take in O2.

CO2 can be an issue if it's so high that it can interfere with O2 exchange(eg high CO2/low O2).

High O2/high CO2 works fine and high O2 and low CO2 works well also.

pH................well, a lot is said, but little is tested............
I think too much is focused on that parameter and not enough of the specific types of salts and ions.

KH will drop in poorly run tanks or non CO2 planted tanks(this is fine in these tanks and expected). Plants will go after the KH if there is not enough CO2 for a given light and nutrient load.

So will algae.

Some bacteria can do this but it's not likely, some in more reductive high organic matter substrates may produce a small amount of HNO3 acid, a strong acid, will decompose KH also.

DIY is not suggested for larger tanks because it tougher to get enough CO2 gas production and to keep it steady. I managed to do a fair job on a 90 gallon tank for several years, but it was a lot of work truth be told and I hardly did much at all after going to a gas tank.
Best $ I ever spent on a planted tanks was buying a gas CO2 system.

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Old 03-12-2007, 09:06 PM   #10
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I agree on the above, a fluctuating ph due to CO2 is no problem at all. As long as your kh remains stable, the ph swings have no ill effects on the fish, unless of course you pump too much CO2 in the tank and hurt the fish. My ph fluctuates from 6.0 during the day to 7.6 at night, no ill-effects to the fish.

As for kh, a swinging kh can be caused by a PWC if your tap is fluctuating, from your water source. But usually it's not enough to be alarmed.
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Old 03-14-2007, 01:02 PM   #11
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hmmm. i found this here too: http://www.drsfostersmith.com/pic/ar...id=328&aid=765
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Old 03-14-2007, 07:56 PM   #12
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Quote:
Originally Posted by galen
This makes several assumptions, that a pH drop due solely to CO2 is in anyway bad, detrimental to fish in FW systems.

I'm not aware that has ever been demonstrated.
Lakes in Florida where they have shallow well planted systems are very often soft water systems can go from 6-10pH every day, they have some of the most productive bass fisheries in the world, in fact, that's why Florida's Bass fishing industry generates 1 Billion$$ a year.

The other issue, when you cite, you should cite the primary research, not a book that's inferred a citation as meaningful.

As far as I am aware, neither Greg nor Diana are fish toxicologist nor have had such trainings.

Such data can be looked up and reviewed.
Then you can make a hypothesis, then you can test that hypothesis and see if you can falsify it or not.

I and many other folks can easily do a large 50-90% weekly weater change on our tanks with enriched CO2.

We do it every week and many have done so for a decade or longer in my case.

pH drops of 1 full unit inside 5 minutes occur in smaller tanks.
Fish are fine, week after week after week, many bred, so neither reproductive, behavioral or any observable stress is implied from such treatments.

The burden of poof should be upon those making such claims.
The observations, the background research, hypothesis when tested and the subsequent results suggest they are not valid.

Note, this is specifically for systems with plants that affect CO2 levels diurnally.

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Old 03-14-2007, 08:15 PM   #13
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When I first hooked up my Compressed tank, I bombed my PH from 7.7 to 6.6 inside of 20 minutes. The fish didn't care (I actually had one come to the surface and tell me)..

The fish really didn't appear any worse or better, but the next day they looked better, only because the plants were producing more O2..

I wasn't sure of the reason that the PH drop didn't bother them, but I can only think that the PH isn't what they react to. So in our happy little triangle of PH, KH, Co2. We know it's not (directly of course) any change in the PH, nor a change in the Co2 levels that bother them. This leaves (by process of elimination) KH. This thought seems to agree with what's above.

I'm sure at some point in soft water, if you drop the PH down to 4 or 3 (almost as low as carbonated soda) the fish will be affected.. But this is just a guess.
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Old 03-16-2007, 02:22 AM   #14
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At the lower end, that's due to the inability to use the pH/KH method to measure CO2, so you might have 30ppm or maybe 300ppm , you will no longer know once you remove the KH............it's no longer an acid base buffer system.

There are indirect methods to measure the CO2, using a KH reference and exchange of the CO2 across a barrier such as an air gap or a membrane(like a O2 probe's membrane).

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Old 03-16-2007, 09:49 AM   #15
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Quote:
Originally Posted by Ketso
Just a few quick questions to help me, if nobdy else, understand what is going on a bit better. What would be the typical cause of a kH change? Everyone seems to be against DIY Co2 in larger tanks because of pH swings. I assumed that this was due, in part, to stressing the fish. Is it really just frowned upon only because of algae problems caused by pH swings?
KH change can come as a result of a mismatch between tank water & water used to replace tankwater during PWCs. This is more likely if you have a mineral sink-condition in your tank or if you add a bunch of buffer salts to your tank but not to your replacement water.

People aren't against DIY CO2 in large tanks because of pH changes, they're against DIY in large tanks because it's difficult (and not cost effective) to do properly. It's tough to maintain adequate CO2 levels in anything much larger than a 20 or 30 gallon tank unless you're using gallons of DIY broth and have a very efficient diffusion method in place. Chronic variations in CO2 (other than day-night differences caused by plants & solenoid switches) tend to promote algae growth (again, not the pH changes shich are typically a matter of tenths of a unit).
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Old 03-17-2007, 10:45 AM   #16
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Quote:
Originally Posted by Plantbrain
Quote:
Originally Posted by galen
This makes several assumptions, that a pH drop due solely to CO2 is in anyway bad, detrimental to fish in FW systems.

I'm not aware that has ever been demonstrated.
Lakes in Florida where they have shallow well planted systems are very often soft water systems can go from 6-10pH every day, they have some of the most productive bass fisheries in the world, in fact, that's why Florida's Bass fishing industry generates 1 Billion$$ a year.

The other issue, when you cite, you should cite the primary research, not a book that's inferred a citation as meaningful.

As far as I am aware, neither Greg nor Diana are fish toxicologist nor have had such trainings.

Such data can be looked up and reviewed.
Then you can make a hypothesis, then you can test that hypothesis and see if you can falsify it or not.

I and many other folks can easily do a large 50-90% weekly weater change on our tanks with enriched CO2.

We do it every week and many have done so for a decade or longer in my case.

pH drops of 1 full unit inside 5 minutes occur in smaller tanks.
Fish are fine, week after week after week, many bred, so neither reproductive, behavioral or any observable stress is implied from such treatments.

The burden of poof should be upon those making such claims.
The observations, the background research, hypothesis when tested and the subsequent results suggest they are not valid.

Note, this is specifically for systems with plants that affect CO2 levels diurnally.

Regards,
Tom Barr
lol. well, i can see now why this forum get's a bad name. plus, since i quoted an article made by someone with a phd in organic chemistry and who is the ceo/president of seachem laboratories, i think they know what they are talking about as they can reproduce exp[eriments and such under controlled conditions. unless your in laboratory, then you cannot make claims that facts are incorrect based upon observations made at home or at work upon systems. therefore, to do so is mistaken and misleading. besides, if you want to see proof, contact seachem and im sure they will send it to you- i will not quote sources from the internet cause i belive that unless that said information is dfone in alab, then it is mistaken. science always beats experience. this is sad- whats worse is faggots online who think they know stuff based upon keeping aquariums for a period of time- you dont so dont question the phds!
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Old 03-17-2007, 11:12 AM   #17
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lol. well, i can see now why this forum get's a bad name. the name of discussion and interaction is a mask for keyboard warriors. now i see why so many warned me about aquariumadvice. its a shame.
And yet here you are, looking to be critical. The intent here is to be constructive and help each other understand a little better. If you have trouble with Mr. Barr and his answer, then do the research and prove him wrong.

IMO he is a scientist who has gone way over and above to help us understand this hobby on a much higher level. Most of us neither have the time or the resources to actually do the research he has already done and been so generous to share.

Discussion and interaction that is misleading is of little use. I know I have posted on issues that I "think" I understand only to have more informed people answer and correct my misunderstandings. If you do not find that valuable, I'm not sure what it is that you are looking for.
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Old 03-17-2007, 11:37 AM   #18
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I see nothing wrong with the article that was linked to at the good doctors. I will request now, at this point, that the conversation be returned to the topic and NOT continue harassment of someone that had the nerve to post a link.

As far as what other peoples warning were about aquariumadvice...that is not productive and that will stop too. If you dont wish to be here, you know where the door is. If you wish to remain...we love to have you.
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Old 03-17-2007, 02:49 PM   #19
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After receiving my lab certified KH solution, I found out that I had been running my CO2 around 100 PPM for months. I do not run the CO2 at night, so I was having major pH changes everyday.

I never lost a fish nor did I notice any ill effects.

I just want to clarify, Tom attacks the idea and NOT the person.
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Old 03-17-2007, 03:11 PM   #20
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lol. well, i can see now why this forum get's a bad name.
I do not believe a forum gets a bad name by questioning things like this topic. Rather, they become wiser and more knowledgeable.

Rather simplistic observations (that any newbie may do) can rationalize such pH shifts are not stressful in the short or long term to fish.
It does not take anything more than common sense to realize that.
Try it an see.

Quote:
plus, since i quoted an article made by someone with a phd in organic chemistry and who is the ceo/president of seachem laboratories, i think they know what they are talking about as they can reproduce exp[eriments and such under controlled conditions.
So where is the "research" that supports your point?
I see none here, some personal feather ruffling is about it.

I offered a simple method to show that it has no impact.
Anyone of us using CO2 can do this. Most have been doing it when they use CO2 and do large frequent water changes. I provided a simple hypothesis that would test for the issue.

Misapplying research and the context when addressing CO2 enriched systems with plants is not the same as fish only systems where pH changes are due to removal of KH and or addition of KH.

Are these the same?
That's what you are suggesting and I will question you about it.
If you cannot stick to the topic without personal jibs, then that reflects right back on you.

A PhD in O chem vs a PhD in aquatic weed research trumps, but it's not about that, it's about the topic at hand. Greg knows his area well, I know mine.

I'm not about that, I'm much more about asking the question based on what you see, observing the results and seeing what conclusions you can draw. Hobbyists can learn a great deal by asking questions and testing for some simple methods to show whether these questions are valid or not.
You do not always require a lab for everything.

That is far better than merely taking someone's word for something.
It also is very helpful to see if such advice applies to the particular case at hand. Generally, labs do not ask the same questions we do here in the hobby. So applying the research is not always easy and seldom good in every case.

Quote:
unless your in laboratory, then you cannot make claims that facts are incorrect based upon observations made at home or at work upon systems.
I do work in a laboratory at the Federal aquatic weed research center in CA, USA.

Even if I did not work in a lab, Paul Sears has a PhD in Organic chemistry, at the time I had no degree 12 years ago, I proved him incorrect, just little old me, showing at home, that adding PO4 to excess levels does not induce algae as he, as well as most others at the time, claimed.
It did not prove what causes algae, it just proved very simply that it could be causing algae. No lab required. Today folks add PO4 to their tanks as a matter of routine, even Amano.

Just because you have a PhD or a lab does not mean you are right.
See PMDD for more of the past issues about PO4.

Quote:
therefore, to do so is mistaken and misleading.
That makes a lot of assumptions without any support.
I have made a hypothesis, tested it, shown results(as many have that do large weekly water changes using CO2), and then discussed it.

Any newbie can do this and see.
Simple, cheap, easy, logical and specific to our case and our question.

Quote:
besides, if you want to see proof, contact seachem and im sure they will send it to you- i will not quote sources from the internet cause i belive that unless that said information is dfone in alab, then it is mistaken.
Such test need to be specific to answer the question at hand: does pH change due to CO2 difference cause fish stress? KH?
That simply was not done and your reference did not support that.

I've addressed that specifically in context of several species of fish, many that are claimed to be sensitive such as shrimp and Altum angels. These are fine week after week after week of 1 full pH unit drops/increases.
Discus breed. Fish grow and live long. So behavior and sublethal effects are not observable near as anyone can tell.

You do not require a lab to see this.
Any newbie can see and do this test, many do weekly as a matter of routine.

Quote:
science always beats experience. this is sad- whats worse is *beep* online who think they know stuff based upon keeping aquariums for a period of time- you dont so dont question the phds!
Science + experience+ testing beats misapplied references for a given situation.

So I cannot not question myself is what you are saying?
<grin>

As a researcher, we question each other all the time. Every person I work with at the lab besides a few under grad p/t interns has one.

<Indulge my "Sarcasm on">
Yes, I'm sometimes am scared to go to work for fear of questioning someone that has a PhD. We get paid to ask questions and see if they are right as best that our feeble minds can rationalize.

You are too funny.

Simply because you have a degree, does not make you an expert in every field. You might find that disconcerting but anyone with such degrees is very well aware of it, except within the field of specialization on what they worked on.

You need to focus specifically on the application in this case. Not some reference that does not apply. I know you felt that it did, but I offered up a lot of simple test to see if this holds true in our specific case.
These test are easy to see that there is more to it that the link provided.

It's like saying adding nitrogen is bad for fish.
What type of Nitrogen(N2, NO3, NH4, NO2, DON) and under what type of conditions(pH, CO2, O2, plants/algae, fish etc)?

Those are extremely relevant questions.

Same deal here.
The devil is in the details.

This is not personal to me, it's obvious that it is for you, it might be wiser to get the ego out of thread and try and learn why specifically this is not the case here rather than poor attempts to poo poo me at a personal level. That only reflects back on you.

Test it yourself and see, then you'll know, no PhD required.

Regards,
Tom Barr
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