how to stop pH swings when using co2

[m-man]

how do you stop the ph from dropping when you are using co2?

 

[Lonewolfblue]

You don't. When injecting CO2, the ph will go down. As long as you are not doing anything to affect your kh, the fish won't be affected by the ph swings. What affects the fish is if the kh shifts and causes ph swings.

 

[mr funktastic]

do u mean keep it from swinging to low? some people will try to bring up there kh in order to keep the ph from bottoming out. but this can be dangerous and inconsistant. u may have to buy a ph controller if u are using pressurised and maybe downsize your DIY system if it is dropping to low.

 

[Plantbrain]

I've not found any evidence to date either in research nor in practical tanks, etc that suggest pH can any issues, even with a KH= 0..

As long as the rate of CO2 add is the same, the tank /plants/fish are still exposed to the same amount of gas, you just cannot measure the CO2 ppm.

You can indirectly by raising the KH up to say 1 degree, then taking the CO2/pH/Kh reading and then doing some water changes to remove the KH again.

But even a KH = 1 is fine.
There is no danger.

Adding lots of KH suddenly is terrible and will kill fish.
But unlike baking soda, a salt, CO2 is not a salt..........

And does not affect fish the same way.
You can add too much CO2 and kill your fish, but that is independent of pH and KH.

Regards,
Tom Barr

 

[mr funktastic]

but injecting to much co2 will casue your ph to swing down to dangerous levels. which can casue fish to die. i thought that the higher KH u had the more resistant your ph was to drop? my co2 is at 50 ppm or higher right now(i dont know exact measurement since i havent done it ina long time) but my fish are fine since my ph is only at about 6.6. but if your kh is to low then it will casue your ph to drop faster with co2 injection wont it? maybe i am miss understanding.

 

[Lonewolfblue]

Before I got my controller, when I injected my CO2, it would go to 6.0 and even 5.8, and I'd slow the bubble rate down to bring it back above 6.0. My kh here is 60. But currently I have my controller set to 6.4-6.6. Even without the controller and the solenoid turning off at night, shutting down the CO2, it did not affect the fish at all, not even going from 7.4 to 5.8, then to 6.2 or 6.3 and then back to 7.4-7.6. As long as the kh remains stable, the fish aren't affected. And as long as you don't have too much CO2 in the water, the fish will be fine. I've heard of people keeping CO2 levels around 100ppm with no side affects to the fish. I used to keep mine at a minimum of 54ppm to a high of around 85ppm, but have since then lowered it to 32ppm to around 45ppm max. It's the kh changes that kill the fish and not the ph swings due to CO2 levels, especially if you are just using the solenoid on a timer between night and day. Will not hurt the fish at all. If you are keeping your CO2 in around the mid 30's, no fish will be affected by swings between day and night.

 

[Wizzard~Of~Ozz]

Incedentally, I believe a large number of tetra's breed in PH 5 water, so I doubt ph alone can cause a major issue. I've dropped my ph 1.2 with Co2 injection fairly quickly (about 1 hr or less) and had no ill effects.

 

[Thebluyak]

so with a co2 PPm of about 35 your not in danger of suffocating the fish?

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

if you go to that site and scroll about half way down it shows a co2-ph chart, and says levels over 25 can be harmful to fish, so im confused as to how a level of over a 100ppms is safe?

 

[Wizzard~Of~Ozz]

Mine is at a constant 37ppm through a PH controller set at 6.5 and a KH of 4.

Fish will not suffocate unless there is no oxygen in the water. Co2 does not displace oxygen last I've heard.

 

[Lonewolfblue]

A CO2 level of 30-35 is what's recommended for plant growth. No, it's not near enough to affect the fish. Some keep theirs even much higher, not sure their reasoning, but still doesn't hurt the fish.

Also, look at it this way. CO2 does not replace O2. They are independant of each other. You can have high CO2 levels and still have enough O2 for the fish. But if too high, the fish might suffer some illeffects from CO2 being too high.

 

[jcarlilesiu]

Ok, Im going to have to pop in here and disagree with whats been said and offer up my recent situation.

maybe some of you remember about a month ago, I inadvertantly killed all my fish but 1. What happened was; i accidentally adjusted my CO2 bubble rate when the tank was turned off for the night. When I recieved the phone call from my girlfriend and went home, I immediatly started doing water tests and water changes to out gas and remove some of the disolved CO2. What I found is why I disagree.

My PH was bottomed out on the master test kit 6.0 or lower. The KH however was still at a 4 or 5 degrees. That reading of my KH is normal for my tank. Yet all the fish died. The one I was able to save was in shock, and from what I understand was in shock due to PH swing. The idea that the KH kills the fish and not the PH swing due to CO2 injection is where my problem is, because in my situation, that isn't what the test results showed.

Soon after my CO2 was turned off, and I verified my KH, the PH slowly started coming up with water changes and filter splash I was doing to help out gas. With out that KH buffering capacity, the PH wouldn't have come back up. that is how I understand it.

Tom, I know you said you can add CO2 too much and kill your fish, but thats independant of a PH KH issue. I was just wondering because of my previous story, what exactly did kill the fish if it wasn't those two?

 

[Purrbox]

so with a co2 PPm of about 35 your not in danger of suffocating the fish?

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

if you go to that site and scroll about half way down it shows a co2-ph chart, and says levels over 25 can be harmful to fish, so im confused as to how a level of over a 100ppms is safe?

Please keep in mind that this article has been around for quite awhile. It's got lots of great info, but people have been playing around with their CO2 levels and found that it's recommended levels are on the conservative side. Lot's of people run their CO2 at 30ppm or higher with no ill affects to their fish. I currently run my CO2 levels between 45ppm and 60ppm and the fish and shrimp are fine. When I had CO2 levels over 100ppm, it was quite another story. I lost a couple of Dwarf Puffers shortly after adding them to the tank, because I didn't realize that the CO2 levels had gone up since my last set of tests.

jcarlilesiu, I suspect that you also lost your fish due to high CO2 levels. With the numbers you provided your CO2 was between 120ppm and 150ppm. If your PH had gone even lower without your being able to test that low, the CO2 levels would have been even higher. This is definately well into dangerously high CO2 levels.

 

[Wizzard~Of~Ozz]

jcarlilesiu,

In your situation you had well over 120ppm Co2. At that level the pure amount will cause organ failure (mainly the gills, they suffocated)

There is an upper limit, but I highly doubt it will be that commonplace. The Co2 level is not really what is being discussed here tho, it's the ph swing that it causes, which I can find no definitive proof of it's harm to fish. (and infact, on an oceanic scale, there is more life present in the very low ph water right by a volcanic eruption then elsewhere.. it's also rich in Co2.)

 

[jcarlilesiu]

Ok, thanks for clearing that up. i was under the assumption that the PH drop killed them, not the CO2 concentration. I must have thought that you can't kill the fish with CO2 like you can't kill them with O2. I guess i was wrong. thanks for the help *scribbles notes

 

[Wizzard~Of~Ozz]

Interesting read if you have the time. http://www.thekrib.com/Plants/CO2/poison.html

Last post on the above link

Hope this helps a bit. You can deduce from this that increased CO2
in the water will not directly prevent hemoglobin in fish from carrying O2, since
Hb does not play a significant role in CO2 transport in fish. However, at
high enough levels CO2 in the water will reduce the diffusion of CO2 from
the blood, resulting in acidosis among a long list of other consequences. I do not
know what behaviour this would illicit, but I do not find it impossible that
the fish would increase respiration, not to obtain more O2, but to get rid
of excess CO2. Since CO2 is so soluble in water, It makes sense that
it would take quite a high concentration to impede diffusion from the gills.

So, in a nutshell. excessive Co2 inhibits the fishes ability to get Co2 out of their system, the is the same as taking extremely shallow breaths.

 

[Lonewolfblue]

Ok, thanks for clearing that up. i was under the assumption that the PH drop killed them, not the CO2 concentration. I must have thought that you can't kill the fish with CO2 like you can't kill them with O2. I guess i was wrong. thanks for the help *scribbles notes

That is the case, yes. Your CO2 levels were well above 120ppm, but probably much higher. I used to keep my CO2 to where it was a minimum of 57ppm and topped at the 80's or low 90's. No ill-effects. But I'm not planning on running tests to see at what point it does start to affect the fish. Would just be too cruel. But now I'm keeping mine down in the 30-50 range, which is more comfortable for me to know they are safe.

 

[SkullJug]

It's intersting how much in this hobby we used to believe is now being proved wrong. This is a really interesting thread, I had no idea and had always been a little worried about PH swings (I use DIY).

It's great to know that as long as KH remains stable I shouldn't have a problem. Correct me if i'm wrong but KH should be stable unless you run short on CO2 and plants start converting Bi-Carbonates??

 

[Lonewolfblue]

I don't think there would be a problem there. People do have planted tanks without CO2, correct?

 

[SkullJug]

Correct - but generally low light. Which Is why I always thought that people advised CO2 injection with more than 2wpg. Anything over that and plants would start chewing KH to photosynthesise??

Yes/ No?

 

[Wizzard~Of~Ozz]

Some plants are adept at using KH for a carbon source, I think Anacharis and Val. are 2. Others will stunt. But overall carbon becomes the major deficiency and algae breaks out. not all plants are good at using a hard form of carbon.