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I am injecting co2 via a pressurized system into a 55 gal. tank. The kh out of the tap is 3 deg. The kh seems to be dropping because when I tested it today it was between 1-2 deg.My question is if I raise my kh with baking soda it will also raise my ph so then will this affect my co2 levels? I mean now my ph is 6.6, so if I add baking soda it will raise my ph and therefore move my co2 reading, won't it? Forgive me for not grasping this concept. Also with a kh of 3 out of the tap, is this lowering of kh over time going to continue to happen in my tank? Can some one also tell me how much baking soda to add and also what kh range should I shoot for.
I also recently started using Kent gh to increase my gh because that is low also out of the tap, I just thougt I'd mention that just incase it matters.
Thanks,
John
 

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Yes, adding baking soda will increase you pH and your KH. My KH out of the tap is only ~2, so I need to add it to keep my pH from going too low with CO2 injection. It's not going to cause a problem for you to add a little bit of baking soda with those pH values as long as you do it gradually.
You may have plants that can consume bicarbonate as a secondary carbon source (vals in particular do this I hear). If that's the case then you might want to add some more to replace the loss or just do more frequent water changes. You don't want the KH to go too low if you have CO2 injection, although you should be fine as long as it's greater than 2 or 3.
However, the only thing that can add CO2 to your water is more CO2. The KH/pH/CO2 relationship is an equilibrium between the bicarbonates and acid produced by CO2.
 

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Yes, KH/PH are linked so raising KH will also raise PH.

Start slow adding Baking soda... Start with a 1/2 teaspoon per 10 gallons, this will add about 2 degrees of KH. I usually dose at night then recheck the KH the nextday, if needed I add more (1/2 teaspoon per 10G per day) until the desired KH level is reached.

When injecting C02 you need a KH of at least 3, if the KH goes below 3 you could have a PH crash.
 

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Trenac,

Since you are a Moderator you must have lots of experience in Buffering. Therefore, explain to me what a PH crash is. I very rarely ever see any reference to it on the Internet forums from a victim. Is this something that 'might' happen but almost never does? What is the chemistry behind this concept?

Andrew Cribb
 

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do u have ph controller if so add kh to the water will not raise the ph it will raise the co2 though

because when u add th kh buffer the co2 controller still will wants to come back to it original setting so then it start adding more co2 to get back down to the 6.6 that was set
 

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pineapple said:
Trenac,

Since you are a Moderator you must have lots of experience in Buffering. Therefore, explain to me what a PH crash is. I very rarely ever see any reference to it on the Internet forums from a victim. Is this something that 'might' happen but almost never does? What is the chemistry behind this concept?

Andrew Cribb
My definition of a "PH crash" is a drastic drop in PH in a short time ( for exp:eek:vernight) due to the lack of KH along with C02 injection or over saturation of C02. Maybe I should have used a less harsh term like "PH swing".

It may be a uncommon occurrence but I did have it happen to me overnight do to over saturation of pressurized C02. Ph drop down to 5 (lowest level on my PH scale), luckily I caught it the next morning before I went to work, I was able to save all my fish (thank goodness).

If you are looking for a scientific discussion that I can not give you, science/biology never was one of my strong subjects. However I do have a general understanding of how it all works. IMO, a strong understanding of science/biology is not needed (but very helpful) to be a a good moderator. I hope you feel the same way.

Here is a couple articles on this subject... http://www.koivet.com/html/articles/articles_details.php?article_id=206
http://www.algae-control.com/crash.html ... although these are talking about ponds.
 

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trenac said:
It may be a uncommon occurrence but I did have it happen to me overnight do to over saturation of pressurized C02. Ph drop down to 5 (lowest level on my PH scale), luckily I caught it the next morning before I went to work, I was able to save all my fish (thank goodness).
Hi trenac,

we are confusing three issues here. Low pH, pH swings and CO2 overdose.

Low pH is not bad for most fish and plants. I can show you plants and happy Tetras living in pH of 4 - 5 for many years.

Swings in pH on the other hand are harmful to both, plants and fish, especially in waters with higher conductivity, higher mineral contents. Either is bad, pH down and also pH up.

CO2 overdose also causes problems, but only to fish. Plants seem to be doing ok in CO2 concentration of 300ppm. I run few tanks with extremely high CO2, without fish of course, and there is no harm nor improvement in plant growth.

Edward
 

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I live in Seattle... and Our water is extremely soft. My kh out of the tap is ussually under 1. I must buffer. On most of my tanks I actually have crushed coral in the filter to help keep my kh levels constant. I also add a little baking soda to my water changes.

To get back to your subject of crashes... I have experienced one. I was just finishing my water changes and had forgot to dose some soda in a heavily planted river tank (sounds funny to have a heavily planted river tank). I was putting away all my supplies and checking on everyone(fish) when I noticed that my river tank's co2 system was bubbling a way. I checked the ph controller and the ph had alreadly dropped to under 5. The controller was set to 6.5. I thought that the controller was malfunctioning, so I checked to see if there was a build up on the ph prob... nothing.. and I then checked the ph controller and recalibrated with ph solution. All was fine... I checked my kh, the kh was 0. I realized that I had not added any soda... I quickly ran and mixed up some baking soda with water and added it to my tank near the intake of my canister filter. The ph controller almost instantly started going up and about 3 minutes later was near normal. This whole ordeal took place in less than an hour. It was very stress full for me... but all the fish seemed fine! I would call what I experienced a CRASH! Not very fun... but I now make sure to buffer all my tanks that have co2 running on them.
 

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turtlehead said:
will adding baking soda be a gradual change in kh?
KH goes up immediately with dose of baking soda. However baking soda NaHCO3 increases Na and conductivity. You can also use Calcium carbonate CaCO3 which takes 2 days to dissolve.

Edward
 

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I was told that coral (calcium carbonate) bits/peices will raise the hardness in my planted tank and that the plants won't like it.

I'm currently using CO2 injection (conservatively- 1 to 1.5 bubbles per sec for a 45 gal tank) sparingly to avoid too much of a drop in pH.

I also have three pieces of Malaysian driftwood in the tank. I'm concerned that it'll lower my pH too much without any source of kh or buffer. I checked the tanks pH last night and it dropped below 6. I immediatly did a 50% water change. (Tanks been setup for 2 weeks now)

Would it be ok for me to add pieces of coral to my H.O.T. Magnum filter to help buffer the water pH level?

Thanks for any help!
 
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