6.6ph and 4KH, no C02 needed? - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 08-12-2015, 07:07 PM Thread Starter
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Question 6.6ph and 4KH, no C02 needed?

There's something I've been a little confused about. I was looking in to adding CO2 to my 55g (because of a cladophora and staghorn outbreak), and wanted to gage how much I might need. Found a few graphs that you measure CO2 by pH and KH, and it shows I have enough CO2 (~30ppm) at my current water parameters. This is new information for me, and I'm a little lost. I've been synthetically constructing my own water from RO/DI to get a 6.6pH, 4KH, and 6GH. Does this mean I don't need to add any CO2 if I do enough water changes?
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post #2 of 9 (permalink) Old 08-12-2015, 07:10 PM
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Dude if you're not adding CO2 then there is no CO2 in your tank. Those graphs are not accurate and should at most be used as a reference point IMO.


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post #3 of 9 (permalink) Old 08-12-2015, 07:26 PM Thread Starter
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Dude if you're not adding CO2 then there is no CO2 in your tank. Those graphs are not accurate and should at most be used as a reference point IMO.
But do the plants in that instance intake the carbonates? Isn't that the purpose of Flourish Excel? Wouldn't the excess carbonates bind with the oxygen present, to form CO2, and that's why many of us see a loss of KH?


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post #4 of 9 (permalink) Old 08-12-2015, 07:45 PM
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Dude if you're not adding CO2 then there is no CO2 in your tank.
That's an exaggeration, and you know it... If it were true, then plants that cannot reap carbon from carbonate would die, rapidly.

That said, the idea that there's 30ppm without injection, particularly after the lights have been on for a while, is absurd.

Atomospheric equilbirium is 3ppm.. resipiration by plants, fish and bacteria can raise it a bit above this, particularly while the lights are off, but not by a factor of 10.

With the lights on, your CO2 is going to be in the low single digits pretty fast, or flatline into zero if you're using too much light.

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Originally Posted by klibs View Post
Those graphs are not accurate and should at most be used as a reference point IMO.
+1.. those graphs assume your water is buffered entirely by carbonates.. no phosphates, no organic acids, etc.

Also, KH, as we measure it with our acid-titration test kits, isn't actually KH.. it is total alkalinity, scaled into carbonate-equivalent units.

New to planted tanks, avid gardener/tinkerer.

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post #5 of 9 (permalink) Old 08-12-2015, 07:58 PM Thread Starter
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Also, KH, as we measure it with our acid-titration test kits, isn't actually KH.. it is total alkalinity, scaled into carbonate-equivalent units.
This I did not know this and that's helpful to know.

Since my source water is in fact pure RO/DI water, and a mix of baking soda for KH, GH buffers, trace minerals, and potassium sulfate. Can I assume my available carbon is high to begin with? Can I get away with just doing a small dose of CO2 (1bps) and have it be effective? I do have a pretty heavily stocked tank, and once I get a refugium hooked up, I'm going to cycle the lights it to help boost CO2 in the daytime.


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post #6 of 9 (permalink) Old 08-12-2015, 08:45 PM
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Due to RO and additional buffering chems chart is no good.
pH tank water then fill a cup and add an air stone for 1 hour.
This will degass any CO2 and test pH again.
Typically every 1.0 rise in pH = 30ppm of CO2.
Let us know your results.


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Last edited by Maryland Guppy; 08-12-2015 at 08:45 PM. Reason: Forgot item
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post #7 of 9 (permalink) Old 08-12-2015, 09:07 PM
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Quote:
Originally Posted by mattinmd View Post
That's an exaggeration, and you know it... If it were true, then plants that cannot reap carbon from carbonate would die, rapidly.

That said, the idea that there's 30ppm without injection, particularly after the lights have been on for a while, is absurd.

Atomospheric equilbirium is 3ppm.. resipiration by plants, fish and bacteria can raise it a bit above this, particularly while the lights are off, but not by a factor of 10.
True - this is what I meant. There is always a little carbon to be used by plants in your water. Just not nearly as much as with a pressurized CO2 setup


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post #8 of 9 (permalink) Old 08-13-2015, 12:58 PM Thread Starter
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Quote:
Originally Posted by Maryland Guppy View Post
Due to RO and additional buffering chems chart is no good.
pH tank water then fill a cup and add an air stone for 1 hour.
This will degass any CO2 and test pH again.
Typically every 1.0 rise in pH = 30ppm of CO2.
Let us know your results.
Done. Measurements read the same. Which doesn't surprise me, as I have a powerhead running to mix the chems for a few nights in a 55g barrel (was having a tough time getting lime to dissolve [and silicate problem] before switching over to using only baking soda).

Should I target a higher pH with my RO mixture and get away with using a DIY or Fluval kit to do a small dose in my 55g tank?
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post #9 of 9 (permalink) Old 08-13-2015, 08:50 PM
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If your substrate doesn't produce CO2, you'd have about 3ppm in your tank. That's how much is in the air. There's a AIR to water conversion.

I doubt you're getting 30ppm from nothing. The kH,pH chart only works in controlled environment. It doesn't account for stuff in your tank that artificially changes the kH&pH.

I have a dirt tank that generates 16-18ppm of CO2.


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Last edited by mistergreen; 08-14-2015 at 12:29 PM.
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