# Will c02 kill fish due to ph changes?



## jamesw (23 Aug 2009)

I understand that putting pressurized c02 into an aquarium will lower the ph of the water. I also read somewhere that it doesnt affect the fish because it doesnt change the kh which is whats is harmfull to fish, is this true? If its going to harm my fish i will not get it, i will be getting a solenoid so i can turn c02 off at nite which obviously means ph will being going up and down every day and night, so im wondering if this is fine for my fish. Thanks


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## Tom (23 Aug 2009)

It will not harm fish as long as you keep it stable. So a solenoid to turn it off at night is a good idea.

[EDIT] by the way I'm selling my reg/solenoid valve on eBay  item number 220468736530 [Mod edit - no direct links ]

Tom


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## Superman (23 Aug 2009)

Most switch off the co2 on the night so that they save co2 gas rather than worry about a pH change.
I'm not a techy in the pH/kH/gH stuff with water and fish but I've never had any problems.
The only problem I've had is pumping too much co2 in there and gasing the fish - so get a drop checker with 4dkH water.

Edit: Nicely done Tom!


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## Themuleous (23 Aug 2009)

Before Ceg jumps in, just to say that pH really doesn't mean much for the kind of fish we are keeping.  I really wouldn't worry about pH.

Sam


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## Tom (23 Aug 2009)

But surely large shifts in pH won't be great, right?


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## Themuleous (23 Aug 2009)

The most co2 will change the pH is by 1 pH point (30ppm = 1pH point drop) that's never going to happen very fast due to the slow rate it dissolves into the water. So called pH crashes are pretty much a myth too.

Sam


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## GreenNeedle (23 Aug 2009)

Think simply:

If your tap water was 7.4ph, tank water 7.2ph and you dosed EI then did your 50% water chane at the end of the photoperiod where the Ph is 6.2-6.4ish then the water change will immediately drive the Ph up very quickly.  For me within 10 minutes.  During that time I have the filter running still so it is very very turbulent water.  Mine will be rising a whole point or so in a maximum of 15 minutes!!!

I only know that my tap is 7.4.  Not tested the tank water but have decreased a little to allow for some acids.  Almost yellow DC.

AC


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## plantbrain (24 Aug 2009)

Basically, CO2 is not a salt, KH is.
Rapid changes in pH due to KH= bad.
Rapid changes in pH due to CO2= does not matter.

Most advice is entirely based on assuming that pH changes only due to salts/KH, not due to change in CO2.
Hence the problem with one dimensional advice and broad applications.

Regards, 
Tom Barr


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## CeeJay (25 Aug 2009)

Hi





			
				plantbrain said:
			
		

> Rapid changes in pH due to KH= bad.
> Rapid changes in pH due to CO2= does not matter.


I didn't know that   . Another little nugget for the memory bank.
Thanks Tom

Chris


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## plantbrain (25 Aug 2009)

chrisr01 said:
			
		

> Hi
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Well, it's one of those things..........advice based on non CO2 enrichment and pH.
Since many things can affect pH, you need to know what it is causing the change, not just the change in and of itself.

Correlation for pH does not tell you what might occur with CO2 enrichment.

A good way of thinking about this is CO2 is not a salt, Carbonate salts, well...obviously are and affect the TDS/conductivity.
CO2 does not comparatively.

In the fish's blood, they already have various levels of CO2(waste) and HCO3(KH).
CO2 is expelled and changed rapidly and easily.
Good thing too. HCO3 levels are maintained differently in fish than CO2.

Same for us.
Fish can take in the HCO3 much much slower and need to adjust to the salts much slower(done in the Kidneys). Osmotic pressure changes. CO2 does not do this(lungs/gills, diffusion).

Oldie, but a good paper for seeing how O2 and CO2 relate with fish.
Yes, I know about Fish Physiology as well as plants  

http://jeb.biologists.org/cgi/reprint/46/2/339.pdf

Covered more here:

http://www.barrreport.com/fish-planted- ... -fish.html

Regards, 
Tom Barr


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## CeeJay (25 Aug 2009)

Great explanations as always   
Thanks Tom.

Chris.


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## plantbrain (27 Aug 2009)

The more folks get and understand this issue, the better.
This helps to prevent the myths and has more folks out there and more eyes to help show what is really going on.
And you learn more about the fish in general and how they work.


Regards, 
Tom Barr


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## Themuleous (27 Aug 2009)

Just out of interest and so I have a sensible answer if I ever get asked, why is there the difference in severity between when CO2 and KH change the pH?  Do we know what actually happens to the fish when the pH changes rapidly due to KH?

Thanks 

Sam


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## baron von bubba (27 Aug 2009)

Themuleous said:
			
		

> Just out of interest and so I have a sensible answer if I ever get asked, why is there the difference in severity between when CO2 and KH change the pH?  Do we know what actually happens to the fish when the pH changes rapidly due to KH?
> 
> Thanks
> 
> Sam



toms post on the first page pretty much covers that.



			
				plantbrain said:
			
		

> chrisr01 said:
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