DIY Co2 and PH

[Ruutah]

Hi everyone, I'm hoping I'm posting this in the right area. I finally got around to fully testing my water earlier today. (I know I'm bad) I've just been using water conditioner and a faucet filter, combined with letting it sit for a few days airing out. But, I found out my water is pretty much liquid rock. As in my ph is between 8.2 and 8.6 using an API master FW kit.

I've read somewhere that using CO2 can lower your PH. I'm hoping someone on here has some experience with it, and can give me an idea on how much.

Thanks!

 

[Caliban07]

Hi everyone, I'm hoping I'm posting this in the right area. I finally got around to fully testing my water earlier today. (I know I'm bad) I've just been using water conditioner and a faucet filter, combined with letting it sit for a few days airing out. But, I found out my water is pretty much liquid rock. As in my ph is between 8.2 and 8.6 using an API master FW kit.

I've read somewhere that using CO2 can lower your PH. I'm hoping someone on here has some experience with it, and can give me an idea on how much.

Thanks!

Yes co2 will lower the ph but this depends on how high your carbonate hardness is. Generally if you have high ph you probably have high general hardness (gh) and high carbonate hardness (kh) general hardness is what tells you if you have 'liquid rock' water as it is mostly the measure of calcium and magnesium in your water. Kh is the water resistance to ph change. This means that if your KH is high you may require more co2 to have an effect on the ph but using high amounts of co2 can be dangerous for our aquatic friends.

You can keep most fish successfully In a ph of 8.2-8.6. If you do consider using co2 then live plants will do well in this tank.


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[PerfectDepth]

Yes co2 will lower the ph but this depends on how high your carbonate hardness is. Generally if you have high ph you probably have high general hardness (gh) and high carbonate hardness (kh) general hardness is what tells you if you have 'liquid rock' water as it is mostly the measure of calcium and magnesium in your water. Kh is the water resistance to ph change. This means that if your KH is high you may require more co2 to have an effect on the ph but using high amounts of co2 can be dangerous for our aquatic friends.

You can keep most fish successfully In a ph of 8.2-8.6. If you do consider using co2 then live plants will do well in this tank.


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Actually KH does not buffer against pH changes due to co2. That's how the ph/KH/co2 relationship works. It takes the same amount of co2 to change the pH regardless of carbonate hardness.

Ruutah, the only reason to add co2 is to grow plants. The pH drop does not make your water softer whatsoever. What you really want to do is lower the KH, which can be achieved by mixing RODI water with your tap water at a ratio that results in the desired KH and ph. Adding things that will leach tannins such as peat, driftwood, Indian almond leaves will also help lower KH/pH.


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[Ruutah]

Got it. I think. I'll reread that a few times to make sure. Any suggestions on test kit for testing Parameters outside those tested with the API kit? (nitrate/nitrite/ammonia/ph/hph)

I'm a big fan of heavily planted tanks. This 10 that I'm working on ( and planning on the diy co2) hopefully will recreate a jungle when it's all said and done. I've got several pieces of Cholla in it, just vertical, as my cories have decided they like being inside of it, and I'm worried they'll get stuck. I guess I need to find an actual piece of driftwood for it.

 

[Delapool]

Now I'm confused

I know kh doesn't change with CO2 injection as have somewhat tested it. I know the CO2 lowers ph and when it stops the ph comes back up.

But I can't figure out how it is doing it. I found this on the web:

============
1) CO2 + H2O > H2CO3
2) H2CO3 > H+ and HCO3-

Then you see that supplying CO2 you are introducing equal amounts of bicarbonates (HCO3-) and H+

http://www.aquaticplantcentral.com/...ion.html#/forumsite/20597/topics/59592?page=1
============

if the CO2 is giving both H+ and HCO3-, how does ph drop?

Is kh test measuring only bicarbonates?


http://www.theaquariumwiki.com/KH

Another link I found;

http://www.advancedaquarist.com/2002/5/chemistry

 

[PerfectDepth]

if the CO2 is giving both H+ and HCO3-, how does ph drop?

Don't forget the greater concentration of hydroxide ions (OH-) since it is a weak acid / strong conjugate base (HCO3-).

 

[Caliban07]

Now I'm confused

I know kh doesn't change with CO2 injection as have somewhat tested it. I know the CO2 lowers ph and when it stops the ph comes back up.

But I can't figure out how it is doing it. I found this on the web:

============
1) CO2 + H2O > H2CO3
2) H2CO3 > H+ and HCO3-

Then you see that supplying CO2 you are introducing equal amounts of bicarbonates (HCO3-) and H+

http://www.aquaticplantcentral.com/...ion.html#/forumsite/20597/topics/59592?page=1
============

if the CO2 is giving both H+ and HCO3-, how does ph drop?

Is kh test measuring only bicarbonates?


http://www.theaquariumwiki.com/KH

Another link I found;

http://www.advancedaquarist.com/2002/5/chemistry

It depends on the acid. When CO2 is the acid you are adding a HCO3 and a H+ from the disassociation of H2CO3 both a conjugate acid and base pair so dKH doesn't fall.

When you add CO2 to water as you know you get:

CO2+H2O

which forms

H2CO3 (carbonic acid)

If we have some alkalinity say bicarbonates (HCO3)

H2CO3 donates a H+ to HCO3 to form

HCO3 + H+

in this case HCO3 has accepted a H+ and has buffered against a ph fall due to added H+

If we continue to add H+ eventually

HCO3 + H+ is exhausted and so H+ accumulate and the H+ -OH ratio tips in favour of H+ and ph falls. Because we are adding H2CO3 which is a H+ donator.

If we have high alkalinity (CO3) and we add H+ CO3 accepts a H+ and disassociate in to

HCO3 and H+. When we run out of CO3 as the buffer ph begins to fall but we still have HCO3 until the same scenario happens and that buffer is used up . So dKH doesn't change when adding CO2 but you can see that high alkalinity does buffer against CO2 and you require more CO2 to change ph.




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