# About Co2 - ph profile



## Lusitanos67 (18 Dec 2019)

Hi,

I think I have problem with something, but I don't know what about Co2.

With kh 1, conductivity 150µS, I can't reach the difference of 1 with the ph profile:
10h40 => pH7.02 Co2 On
11h40 => pH6.70
15h40 => pH6.40
17h40 => pH7.25
19h15 => pH6.25

And I try to obtain pH6.02 maybe 2 hours after Co2 start, that's correct ?
Can you help me to optimize Co2 diffusion (tank about 250L) ?

1st Video to show my diffusing system:


and this to check potential leaks:




Thank you


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## jaypeecee (18 Dec 2019)

Hi @Lusitanos67

I seem to be a lone voice on UKAPS but I'm unhappy with this 1pH drop 'requirement'. It is further complicated by assuming that the standard pH/KH/CO2 table is accurate and reliable. Please see:

https://www.ukaps.org/forum/threads/why-advise-a-1ph-drop.58798/

My concern relates to the toxicity of CO2 to fish and, perhaps, other critters. If your tank is plants only, then that's different.

JPC


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## Zeus. (19 Dec 2019)

Lusitanos67 said:


> And I try to obtain pH6.02 maybe 2 hours after Co2 start, that's correct ?



Yes - 2 to 3 hours is about normal for most tanks the bigger the pH drop the longer it takes. But the Nine hours to get 0.75 pH drop is just down to not getting enough CO2 into the tank water. 

your BPS seems a bit on the low side for a 250l tank

Hers the BPS for my 500l


I do manage to get my pH drop of over 1.0pH in about 30mins - but use duel CO2 injection for the pH drop period. The vid shows I take no prisoners when I inject the CO2

The 2hr Aquarist - by D Wong has a great section on CO2


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## jaypeecee (19 Dec 2019)

Zeus. said:


> I do manage to get my pH drop of over 1.0pH in about 30mins - but use duel CO2 injection for the pH drop period. The vid shows I take no prisoners when I inject the CO2



Hi @Zeus. 

OK, in that case, it raises a question or two. A pH drop of over 1.0 means that CO2 concentration is increasing more than tenfold. As you know, the pH scale is logarithmic to base 10. Therefore a 1.0 pH drop is a 10^1 = 10x increase in CO2 concentration (assuming that KH remains constant). So, if the starting CO2 concentration is 3ppm, then the final CO2 concentration will be 30ppm, which would be the recommended maximum for fish. But, if (for example) the starting CO2 concentration is 6ppm, then the final CO2 concentration will be 60ppm, which would normally be considered to be toxic to fish. So, either:

1 Your starting CO2 concentration is less than 3ppm

2 Can fish 'tolerate' CO2 concentrations in excess of 30ppm?

3 Maximum permissible CO2 concentration varies with dissolved oxygen concentration

4 KH is not constant

5 Some other explanation

I would greatly appreciate any comments that you or others may have. Is my reasoning flawed?

JPC


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## Lusitanos67 (20 Dec 2019)

I will try with little more Co2.
Thank you for videos and thoses details


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## Zeus. (21 Dec 2019)

jaypeecee said:


> OK, in that case, it raises a question or two. A pH drop of over 1.0 means that CO2 concentration is increasing more than tenfold. As you know, the pH scale is logarithmic to base 10. Therefore a 1.0 pH drop is a 10^1 = 10x increase in CO2 concentration (assuming that KH remains constant). So, if the starting CO2 concentration is 3ppm, then the final CO2 concentration will be 30ppm, which would be the recommended maximum for fish



Correct 



jaypeecee said:


> But, if (for example) the starting CO2 concentration is 6ppm, then the final CO2 concentration will be 60ppm, which would normally be considered to be toxic to fish.



Correct again in the first part but not necessary toxic to all livestock.



jaypeecee said:


> Can fish 'tolerate' CO2 concentrations in excess of 30ppm?



Yes IMO/IME my Harlequin Rasboras seem to more sensitive to high [CO2] these I have gasping for air towards the end of the pH drop and also if fed during main CO2 period they would go belly up in the excitement of a feeding frenzy and recover a few mins later (DC would be nearly clear at the time - I have since reduced my pH drop for other reasons).
As for the pH drop as @ceg4048 quotes here he typically had a pH drop of 1.2pH, think mine is excess of 1.2pH drop even ATM but the inmates don't have any issues with it as far as I'm aware



jaypeecee said:


> Is my reasoning flawed?



Nope - we all have to work with what we a comfortable with and what we think/believe is safe for our tanks inmates without causing unnecessary stress. eg feeding my Harlequin Rasboras when CO2 was off resolved them going belly up


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## jaypeecee (22 Dec 2019)

Hi @Zeus.

Many thanks for your reply. Based on your valued feedback, *advising people to aim for a 1.0 pH drop should come with a warning*. You have demonstrated this with Harlequin Rasboras. Why put your precious fish at risk for faster plant growth? Even 'inmates' can say 'no' but fish end up 'gasping for air' or go 'belly up' instead.

JPC


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## Zeus. (22 Dec 2019)

Well my pH drop is still over 1.0pH and I don't have any fish showing any signs of distress or gasping even when I drop the pH in just over 30mins. Added 30 amanos 20 tetras and six corys on Saturday non have show any issues and I didnt change the injection rate. Think I was doing about 1.4pH drop when the Harlequin Rasboras had some issues (never lost one all the same).

So I have no issues advising a pH drop of 1.0pH. Any higher is always a potential risk if something fails

 I did lose a few RCS on 50l as a forget to clean the eheim skimmer before holiday - clogged up - bio film on tank - reduced flow- increase [CO2] 

I have lost more inmates from jumping out of tank even with glass lids than I have had with CO2 on 500l
Lost more Amanos with open top tank than with CO2.

How many folk have lost inmates with end of tank dump with single stage reg?


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## jaypeecee (23 Dec 2019)

Zeus. said:


> I have lost more inmates from jumping out of tank even with glass lids than I have had with CO2 on 500l
> 
> Lost more Amanos with open top tank than with CO2.
> 
> How many folk have lost inmates with end of tank dump with single stage reg?



Hi @Zeus. 

None of the above are relevant to this thread and all can be mitigated against.

JPC


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## Zeus. (24 Dec 2019)

jaypeecee said:


> Hi @Zeus.
> 
> None of the above are relevant to this thread and all can be mitigated against.
> 
> JPC



True, however my loses have been more with non CO2 related incidents and yes if CO2 is done wrong the results can be catastrophic so great care and diligence is needed with injecting CO2 and dont take the DC passed green for the novice


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