need help to adjust co2

[Patrice]

hi,
with no co2, I have a ph of around 6.2 and kh 4
i try to get close to 30 ppm of co2 but according to the chart i found on internet, i am not gona get it. if inject i buble/sec of Co2, I now have ph of 5.8 to 6 and kh 4 so it's to mutch co2 (according to the chart)


what should i do?

 

[Tom Barr]

See the pH drop checker Vaughn suggest here and the KH reference solution.
We both know that the CO2 is not what it is according to the chart obviously.

Regards,
Tom Barr

 

[Patrice]

I have add cooked baking soda to get my kh higher thinking my ph would follow. it's way to acid in that tank. So the kh went from 4 to 8 but ph is still the same. Was i wrong thinking ph would rise up?

 

[sevenrider860]

I believe that baking soda will increase your KH without affecting the pH.

Brian

 

[Patrice]

yeah, this is what's happening. so what should I do to inject Co2 without having à ph under 6?

 

[sevenrider860]

I don't worry about my pH, so I can't give much of a suggestion...sorry. I keep my GH and KH between 3 and 5 and try to keep about 30ppm CO2 during the day. When the lights go out my pH rises when the lights come on it goes back down. None of my fish look like they are bothered.

I have seen suggestions on raising pH, but again I have never used them.

- Filter over coral or limestone
- Add rocks containing limestone to the tank or use a coral sand substrate
- Use a commercial alkaline buffer

Brian

 

[Patrice]

I have some PH buffer 8.3 here. Maybe I should try that.
also, if I get my GH up a little (It turns at the first drop in my test kit) do you think It would help rising the ph?

 

[Tom Barr]

If you have low KH and add bakign soda, your pH should go up all other things being equal, if the KH is 3 and you raise it to 6 etc.
Sounds like a lousy pH test kit or a bad KH test kit.

Test the KH out on a DI water smaple, slowly add more baking soda and the pH should buffer to about 8.1-8.3 range or so as you add more.

Regards,
Tom Barr

 

[Patrice]

bad test kit... humm...
for ph, I suse a hanna probe.
for kh i use hagen test kit

my kh went from 4 to 8 with baking soda (cooked baking soda, forgot the english name for this). At the end of the day, ph was still the same. maybe I should have wait a little longer before to test ph?
Will it have any isue if I raise kh to mutch?

 

[JoeBanks]

(cooked baking soda, forgot the english name for this).

This may be your problem.

Are you referring to baking powder?

Baking powder is baking soda plus an acidifying agent which would explain KH going up and PH staying the same.

 

[VaughnH]

This may be your problem.

Are you referring to baking powder?

Baking powder is baking soda plus an acidifying agent which would explain KH going up and PH staying the same.

I usually cringe when some of us refer to it as "baking soda". We should be saying "bicarbonate of soda", or "sodium bicarbonate". Then there would be no confusion. And, there is no reason to bake bicarbonate of soda unless you are depending on measuring a specific weight to be added to get a specific KH. Since it absorbs water it can consist of almost as much water as sodium bicarbonate when you measure out a few grams of it. Baking it drives off the water, leaving nearly pure bicarbonate of soda.

 

[Patrice]

I usually cringe when some of us refer to it as "baking soda". We should be saying "bicarbonate of soda", or "sodium bicarbonate". Then there would be no confusion. And, there is no reason to bake bicarbonate of soda unless you are depending on measuring a specific weight to be added to get a specific KH. Since it absorbs water it can consist of almost as much water as sodium bicarbonate when you measure out a few grams of it. Baking it drives off the water, leaving nearly pure bicarbonate of soda.

thats thrue, we should call things by there names to not be confused. sometime I have that problem with english (forget words all the time).
What I used was carbonate of soda. I used the recipe Tom gave to make a kh ref solution on the post about the ph drop checker.

so it could be the reason why kh goes up and not the ph?

thx for your help

 

[VaughnH]

Something is amiss. If you have X ppm of CO2 dissolved in water, and add bicarbonate of soda to raise the KH, the pH will have to go up too, unless the ppm of CO2 drops at the same time. One possible answer is that the KH you get with added sodium bicarbonate is not stable immediately. If you measure KH right after adding it, you get a higher number than if you wait a few hours and remeasure it. I am not a chemist, so I don't know why that is true.

 

[Patrice]

thx I'll make a few more try. by the way, do you know what quantities of bicarbonate of soda it's need to increase the kh value in a certain volume?

 

[JoeBanks]

Check here:

Buffering capacity and pH

 

[Patrice]

great toll! thank you!

 

[Patrice]

I'me glad and sad at the same time.

sad beacause I have test how good is my kh test kit and it showed that this nutrafin test kit is off by 3.
Glad beacause I found out about it. beter later than never.

now, I am gonna get a new test kit! a good one this time!

 

[Patrice]

great! it worked! I raised my kh by 4 and the ph went up.... a little!

so I know have a kh of 7.5 for a ph of 5.6 (was 5.5 before so no big change). I'll wait until tomorow and see if ph goes up a little more like it should be (according to the link you gave me).
by the way, what should be the kh limit to reach? I like to make experience but do not want to kill what's in the tank.

 

[girthvader]

thats odd. when I have used baking soda in the past it raises the ph as well as the kh. eg. In my 90g with a ph of 6.2 and a low kh of 3 I used a measured 7 tspns and my kh went up to 8 and my ph up to 7.4 . also 5.6 seems pretty low especially for fish. I would think your fish to be stressed at that level. I know when I have turned up my CO2 to anythything above 40ppm with a PH of 6 I see dramatic stress to the fish, to the point of laying on the bottom on their side. So I keep my CO2 at 35ppm and PH of 6.8. fish seem fine and the plants are happy.

 

[Patrice]

there is no fish in this tank and it's a co2 tank. I have dose more bicarbonate of sodium and my kh went up lot but the ph did not follow as I thought.