A Ph/co2 Question

[fishboytoo]

Hello plant Guru's,

I was hoping some of you could clarify something for me.

I have some Seachem Acid Buffer which the guy at the LFS said would help me get my CO2 levels higher. It says on the bottle that it "converts carbonate alkalinity(KH) into available CO2". I recall reading somewhere on here that buffers don't actually raise CO2 levels. Does anyone know if this is actually raising my CO2 or just droping pH? I do get lower kH values when I use it.

I have fairly hard water at 160mg/L CaCO3 and a DIY injection system. This buffer is the only way I can get a substatial drop in pH=rise in CO2.

I am also having difficulty getting consistant levels of CO2. I use two bottles and rotate changing them out. I get about 20-25 bubbles per minute into the intake of my HOB power filter. Is there anything else I can do/change here to make this economical system more effective?

I am getting frustrated with trying to control this. I would really appreciate some advice.

Thanks FB2

 

[IovaykInD]

Changing the pH will in turn change the KH, it won't change the co2. The only way of adding co2 is by adding co2 via co2 bubbles.

I had that idea a while back too, when I first got into planted tanks
Read this:
http/www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

 

[Themuleous]

Hi,

First off read that link it'll expain it better then I can, but i will give it a go all the same.

When it comes to pH/CO2/KH the relationship is such that if you change either KH or CO2 the pH will change. It is pH that is the resulting variable in the whole situation. Generally speaking if you lower KH you also lower pH, if you increase CO2 you lower pH. You can not increase KH and expect to have more CO2 into the water and conversely, you cant lower pH and expect to get more CO2 into the water. Thats not how it works.

If you do not already add CO2 then this relationship does not work.

As for the acid buffer adding CO2 by converting the carbonate to CO2, i would think not, for this to happen, the carbonate is going to need to have its carbon atoms removed and combined with oxygen in the water, I doubt an acid will do this, although Im not 100% sure on that, but thats my feeling anyway. The only way to get more CO2 into the water is to increase the amount you pump in, simple as that.

Hope this helps

Sam

 

[fishboytoo]

As for the acid buffer adding CO2 by converting the carbonate to CO2, i would think not, for this to happen, the carbonate is going to need to have its carbon atoms removed and combined with oxygen in the water, I doubt an acid will do this, although Im not 100% sure on that, but thats my feeling anyway. The only way to get more CO2 into the water is to increase the amount you pump in, simple as that

It didn't really seem reasonable to think that this alteration of pH would add CO2, however there are tiny bubbles released as the granules dissolve in the water. That, and the bottle specifically says it increases available co2 made me wonder whether it was possible.

Perhaps the buffer converts the carbonate into carbonic acid thereby lowering pH and making co2 available for plant use. Carbonic acid, in water, readily breaks down into co2 and water, according to http/www.newton.dep.anl.gov/askasci/chem99/chem99661.htm
I can't tell specifically what reactions are taking place without knowing what the buffer actually is (ie. phosphate). Really makes me wonder though. I would like to study it further.

Again, it all doesn't seem likely. How can Seachem make these assertions then? Someone should sue them for false advertising.

Thanks for the link, that's a good article.

Chris

 

[TwoTankAmin]

Basically, if you have surface aggitation in the tank, the water will equalize in terms of co2 and O content with that of the air. If you want to increase co2 level w/o adding gas, you can arrange filtration so that there is no surface aggitation. However, unless you are over stocked and under or non-planted, there is a limit to how high co2 levels can get.

Co2 lowers pH-

One safe way to lower pH WITHOUT adjusting KH is to bubble CO2 (carbon dioxide) through the tank. The CO2 dissolves in water, and some of it forms carbonic acid. The formation of acid lowers the pH. Of course, in order for this approach to be practical, a steady source of CO2 bubbles (e.g. a CO2 tank) is needed to hold the pH in place. As soon as the CO2 is gone, the pH bounces back to its previous value.

from the FINS site http/fins.actwin.com/aquariafaq.html

 

[vic]

Introducing the DIY CO2 through the HOB is not likely the most efficient method. The deffusion rate is likely quite low as the CO2 bearing water is introduced at the surface and the CO2 is likely escaping into the atmosphere rather than being disolved in the tank water. I would suggest that you investigate CO2 diffusers on the internet. There are a number of them out there including the Hagen CO2 ladder. There are also a number of DIY options as well. Another option, the one I selected, is a small power filter by Elite (Hagen). This is a 3 gal submersabile filter that has an exhaust direction control and a inlet port for an air line. Simply place the filter as low as possible in the tank and away from any filter pickup, connect the DIY CO2 line to the little filter and let it rip. You will get far supperior diffusion of the CO2 at a very low cost. The filter was $15CAD.

US Peco website http/www.petco.com/Shop/Product.aspx?familyid=13796

 

[fishboytoo]

Thanks Vic,
I have looked into a ladder and the powerhead with a venturi intake was recommended instead. I read about running the co2 into the power filter intake and thought i'd give it a try before buying more gadgets. I suppose I may have to give in and buy one, but I'd hate to have that not work for me also. Then I'll have to go to a pressurized system anyway after having spent all my money on the other options first. It's driving me nuts already.

Where did you get your powerhead? Order it from the states or LFS?

And Twotank,
I keep the water level as high as possible to reduce surface agitation and i can see tiny bubbles being release from the returning water. It's just not enough i guess. I have been told I'm overstocked(and overfiltered) but not under-planted.

Thanks for the replies