pH profile change

[MikeG747]

Hi,

I am trying to work out what a sensible pH profile change is so that I can maintain optimal CO2 levels in the tank. I have a drop checker in the tank, but telling the difference between shades of green is challenging.

To start with my tank pH is currently around 5.5 (without CO2), my tap water has a pH of around 7.4 and GH of around 9. The tank pH is so low due to ADA malaya and africana substrate in the tank.

I know that pH is a logarithmic scale so I am guessing that a drop of 1 pH point would be rather extreme.

So what kind of drop should I be looking for to maintain ~30ppm CO2?

Thanks

Mike

 

[Edvet]

I think you would still need a 1 point drop, with softer water you'll need a bigger drop.http://www.ukaps.org/forum/threads/quick-question-co2-kh.31934/

 

[Spnl]

"I know that pH is a logarithmic scale so I am guessing that a drop of 1 pH point would be rather extreme."

I think you are right. If you look at the co2/pH/KH chart on the Barr report it doesn't go below pH 6, which might tell you something in itself. You don't say what you KH is, but say it is about 4 (probably not less given the GH), to drop the pH from 7 to 6 you would need to add over 100ppm CO2! To go from 6 to 5 will need 10x that! Now, these numbers cannot be real, but even if just ball park figures that is a lot of CO2.

I suggest you use the drop checker to set your target, note the pH when it is yellowish green, and aim to get there before turning the lights on. That gives you your profile. pH changes are great for monitoring the effects of changes to CO2 injection, but the 1 point drop is just an estimate of how much is needed under normal conditions. For most of us a starting pH of 5.5 is certainly not normal (unfortunately).

 

[Mr. Teapot]

Maybe your CO2 hasn’t fully degassed before taking your pH reading. I was really surprised at how long it took for my tank to degas all the injected CO2. I only managed to get a stable reading after leaving a glass of tank water standing for 48hrs.

 

[Spnl]

Oh, forgot to add, I don't think you could drop your pH from 5.5 to 4.5 using CO2, not at atmospheric pressure anyway

 

[pepedopolous]

Maybe your CO2 hasn’t fully degassed before taking your pH reading. I was really surprised at how long it took for my tank to degas all the injected CO2. I only managed to get a stable reading after leaving a glass of tank water standing for 48hrs.

I agree with this. I don't think your soil would reduce the pH so much on it's own.

P

 

[MikeG747]

Thanks for the replies everyone. It has confirmed my suspicions that using a pH drop of 1 point would have fatal consequences. I think I shall use my eyes as a guide for the CO2 levels. If I start seeing unhappy fish then it is too high, if I start seeing algae then it is possibly too low or I have dodgy distribution.