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Gang,

By chance, I came across a link called [link=Chuck's Planted Aquarium Pages]http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm" style="COLOR: #ff6633[/link] that Bablefish provided (thanks Babel ).

While skimming through that site, I discovered an explanation regarding the relationship between CO2, ph, and
KH. Although I have read many peaces of information about this topic, it seems to me that I understand it for
the first time.

I would like you to tell me if I got that right.

1) The relationship and it’s consequences for the planted tank are only valid if no additional non-carbonate
buffers are added to the water. Non-carbonates are for example phosphates.
2) Without the addition of carbonate buffers, the only entity here that can be influenced is the CO2 via injection
etc.
3) Assuming that 1 and 2 are correct, am I right (see the chart image below, also from this site) to conclude that
having a ph of 6.8 and a KH of 0.5 would result in a ph of 6.0 when adding CO2 to reach 15 ppm?

That would not be good. I know that baking soda is a buffer to raise the KH, but is it carbonate based?
How could I achieve a 15ppm CO2 level and still maintain a ph of around 6.8?

Thanks,

Ingo


Little_Fish attached this image:

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Proud Member of the New Jersey Aquatic Gardeners Club

"1) The relationship and it’s consequences for the planted tank are only valid if no additional non-carbonate
buffers are added to the water. Non-carbonates are for example phosphates."

Phosphate buffers change your pH without changing your KH or CO2 levels. For instance, if your pH is 6.8 and you use a phosphate based buffer to raise it to 7.4, your KH will still be 0.5 dKH and your CO2 levels will still be somewhere around the equilibrium of 4ppm CO2, but if you will consult the table it will look as if you're CO2 levels have dropped, which is not true. In that sense, the table becomes invalid.

Basically, raising your KH (referred to often as buffering capacity, and is what you call carbonat buffers) will raise your pH. Adding CO2 will lower your pH. This is still true when phosphate buffers are present in the water, it just means that the table is useless because the pH reading you will get is affected by the phosphate buffers.

"2) Without the addition of carbonate buffers, the only entity here that can be influenced is the CO2 via injection
etc."

I don't really understand the question, but I think the answer is yes. Changing your KH and/or CO2 concentration will change your pH. Chaing your pH by using phosphate buffers will not change your KH or CO2 concentration.

3) Assuming that 1 and 2 are correct, am I right (see the chart image below, also from this site) to conclude that having a ph of 6.8 and a KH of 0.5 would result in a ph of 6.0 when adding CO2 to reach 15 ppm?

Yes. If you want your pH to be around 6.8 and your CO2 level around 15ppm, then you need to raise your KH to 3 dKH. And yes, one way to do it is by adding baking soda to your tank, which is carbonate based. With your current KH/pH/CO2 levels, raising the KH to 3 dKH will raise your pH to about 7.6. When you add CO2 at 15ppm it will go down to 6.8.

Once you raise your tank water to 3dKh you will also have to add baking soda to the water you use for water changes to bring it to 3dKH, of course, or your KH will go down in time and with it your pH.

To sum it all up, what you're aiming for is to raise your KH to 3 dKH (by adding baking soda) and adding enough CO2 to bring your pH to 6.8 (which means your CO2 levels will be at 15ppm).

I hope this is clear enough and helps. Ask away if you have any more questions.

untitled,

Yes, your answer is clear enough and I really appreciate your patience explaining this relationship to me.

Now, this leaves me with one additional question (or two), if you don’t mind:

Is there a simple formula how much baking soda would have to be added to a tank in order to raise the ph, for example in tsp / gallon? I would assume that not, given that the gap between (for example) 6 and 6.5 is not the same than the one from 6.5 to 7.

What are the practical steps when adding baking soda initially, and during water changes?

Thank you again for your response,

Ingo

Last edited by LITTLE_FISH at 16-Jul-2005 05:28

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Proud Member of the New Jersey Aquatic Gardeners Club

This is definitely not a formula, just a rough guide line, but 1 teaspoon of baking soda per 10 gallons will raise the KH in 4 dKH. Again, this is very roughly. It's basically trial and error, but we try the error to be on the safe side, i.e. not raising the KH too much at once.

The practical steps:

For the the tank, add enough baking soda to raise your KH in about 1 dKH (i.e. 1tsp per 40 gallons), wait a few hours and test your tank water and see how much the KH was raised. If more than 1, put a little less next time, if less than 1, put a little more. Add the next dosage the next day and repeat it until you reach a reading of 3 dKH. Your tank is then set.

As for water changes, you can either add the proportional amount of what you used initially (i.e. if you added 4 tsps altogether and you change a quarter of your tank water, you will need 1 tsp). Or, if you change using a bucket, just fill your bucket and add enough to baking soda to bring it up to 3 dKH (i.e. add a little bit, mix the water, wait, test, repeat if necessary) and you will know how much tsps of baking soda you need per bucket. Or you can come up with something else altogether. After a while you will get the hange of it and will not have to test it anymore.

In any case, adding CO2 is not such a big deal as it might sometimes seem to be. It's basically making sure that your KH is not too low and then adding CO2 to your desired target (and many of us here aim at more than 15ppm, by the way, to something around 30ppm) and then taking care of your plants. We pretend it's complicated on internet forums because we want to keep it an exclusive club, but once you've got the idea of what's going on, it's no brain surgery, as someone I once knew used to say...

untitled,

Thank you so much for your instructions on how to use the Baking Soda.

[font color="#000080"]We pretend it's complicated on internet forums because we want to keep it an exclusive club, but once you've got the idea of what's going on, it's no brain surgery[/font]

Well, if I will succeed with my CO2 system and the ph regulation, would I have to wear a suit and tie to get into this exclusive club?

Again, thanks a lot,

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club

Well, if I will succeed with my CO2 system and the ph regulation, would I have to wear a suit and tie to get into this exclusive club?

No, I think the acceptable uniform is a old shirt covered in Kno3 an PO4 stains , a planting tweezers in the shirt pocket, bottle of TMG in the back trousers pockets, the Ph/KH chart tatooed on your chest and if you're feeling adventurous a couple of bubble counters as ear rings

]

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Some days you're the pigeon and some days you're the statue.

Remember that age and treachery will always triumph over youth and ability.

Bensaf, is that how you do it in Ireland??? Here in England we have to wear the latest Parisian fashion before we tend to our tanks. It might sound glamourous but trust me, it's no picnic doing your water changes on high heels, although it does help reaching further into the dark corners of the tank.

Ingo, as to your question, you will have to check the regulations of the American branch of the our secret organisation. It's such a big secret that we don't even have a name so people can't look us up on google. However, you can always recognise us by the TMG bottle in the back pocket, as Bensaf revealed, and by the strange looks we give to any body of water (even puddles) to see if there's anything in there that we can nick to use in our tanks...

bensaf and untitled,

Given that we in the US are a blend of many cultures, I guess I will have to be on the lookout for someone with PH/KH chart on his forehead, no clothes at all, and high heels.

But just in case, I will try to become friends with Frank and Keith, as these two for sure know who I will have to talk to regarding a possible membership.

Thanks for this information; I am now constantly looking over my shoulders and try to spot one of them.

Ingo

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Proud Member of the New Jersey Aquatic Gardeners Club