co2 and ph help

[Linariel]

So my kh is at 11. Does this mean I need less co2 (in bubbles per second) than someone with a lower kh? I'm having a hard time getting it right. My ph dropped a full point, but I checked the charts and that appears to be too much.

I though all aquariums needed a full point drop in ph, but since my kh is so high this means there is too much co2, right?

Thanks.

 

[Squawkbert]

Add CO2 slowly. 1 unit for KH 11 may be too much.

Best way: Drop checker. They're KH independent (tank water KH that is).

Plenty of posts here & @ APC about them.

 

[Linariel]

I don't have any fish or plants right now so I just dumped a bunch in. I thought it was a full point drop for all tanks so I set it for about 3 bubbles per second.

I just wanted to make sure I had it right, that high kh needs less co2 to reach the desire ppm.

Thanks for the tip about the drop checker, I'd never heard of one before. I'll do a search for them.

 

[Rex Grigg]

The full point drop still holds. No matter what the KH. The higher the KH the more resistant the water is to changing.

 

[Linariel]

Rex, your guide has been very helpful to me, thanks for maintaining it. And that makes a lot of sense.

I re-tested everything and I believe my original ph test was incorrect-my water is 8.0 and my tank is now 7.0. That's slightly in the red on the co2 chart, so I will make a minor adjustment.

 

[loaches r cool]

...-my water is 8.0 and my tank is now 7.0.

What do you mean by that, your tap water is 8 and tank is 7, or tank was 8 and now is 7. That could make a bit of a difference.

 

[Linariel]

Tank was 8 after sitting for a few days with no co2, and is now 7 with co2 injection.

 

[loaches r cool]

That should be ok then, assuming your tests are accurate. BTW KH will not affect CO2 levels, they are two different things. KH will affect you pH level however. The only way to to raise or lower CO2 levels is to put in or take out CO2. KH and pH changes can be the result of CO2 but not the cause if you get what I'm saying.

 

[Linariel]

I have an API master liquid test kit, so I think they're accurate.
I think I understand. But my KH has not changed since adding co2-is that normal? Or should I have both a KH and pH change?

As soon as I think I understand this stuff...!

 

[phanmc]

CO2 does not affect your kH.

CO2 affects your pH because it forms a weak acid when it dissolves into water, and the pH is a measure of how acidic or alkaline your water is.

The pH/kH chart assumes that the kH is the only buffer against acidity in your tank and the CO2 is the only acid being put into the tank. If you have other buffers like phosphate and acids like tannic acid from driftwood, then the reading won't be accurate.

The 1pt pH drop is a pretty good ballpark. For a more accurate reading, a drop checker with a pH indicator solution is most accurate.

Water with a high kH needs the same amount of CO2 as a water with a low kH. The only way to get more CO2 into your water is by injecting it, and not playing around with your pH/kH via other means.