# pH, KH, Co2 Question



## dynafire (Dec 19, 2007)

Hello fellow hobbyist,

I am fairly new to aquatic plants and not to mention co2. I have a situation that I would like some input to clear it up. Let me apologize if they have been answered in other threads, but here is my situation: 

1: My tap water param: pH:7.5, KH:2dH, NO2-:0ppm, NO3-:0ppm, NH3/NH4+:0ppm

2. The tank is a 29g display tank but it is connected to 20g tank so the total water volume is ~50g. I will be dosing PPS-Pro so that would be 5ml of each solution (correct me if i'm wrong).

3. Here is the real problem: I am try to get my co2 level to around 30ppm, but in order to do that I need to put enough co2 into the aquarium so that my pH drop to around 6.3. It is about 1.2 pH difference from my tap water if I were to do water changes. It would be quite a bit of pH swing for the fishes right? 

So my question is: How would I achieve my goal with little stress to the fishes as possible?

Thanks in advance,
David


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## Zapins (Jul 28, 2004)

The fish won't get stressed from a pH drop of 1.2 especially if you add CO2 slowly. If you change the pH over night things will be just fine.

Also, since your KH is very low you won't have to add much CO2 to get a fast pH drop. KH acts as a buffer, so when acids or bases are added to the water they bind to them and neutralize them. Since you don't have a lot of buffering the pH will change after adding a relatively small amount of CO2 (i.e. it will change quickly). 

Additionally, the fish will probably be more stressed by the CO2 than by the drop in pH. In nature water often drops in pH rather quickly when it rains (rainwater is 5.5-6 pH). CO2 stressed fish will gasp at the surface for air. If you see this, just add a bubbler to reduce the CO2 in the water (or rather, increase the O2). Over a period of a week the fish will adapt to higher CO2 conditions and stop gasping at the same level of CO2, so you can slowly increase the CO2 concentration to insane levels depending on where you want to keep it.


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## ray-the-pilot (May 14, 2008)

The only way to do that would to be to use a CO2 controller. 
CO2 controllers use the pH change caused by the addition of CO2 to regulate the amount of CO2 added. 

While I doubt that a pH change of 1.2 would effect your fish much if the only thing that was changing was the H+ concentration; the problem with a 1.2 change in pH caused by CO2 is that change corresponds to a change in CO2 of 16X. Or the CO2 in your tanks will go from 5 ppm to 80 ppm. I really don’t think that is healthy. (but that is my opinion). 

My experience is that some fish will show a decline in activity at 30 ppm. I keep my level at 20 ppm. I have no problem growing plants but I suppose that I accept a higher level of algae in my tanks. My goal is a natural environment not a garden. 

The solution volumes that you are adding are correct. I’ve been using PPS-Pro in my setup for over a year but I still do 20% water changes each week. I also regularly test for KPN and adjust my additions based on the results.


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## BryceM (Nov 6, 2005)

Rather than get too worked up about particular CO2 numbers, the pH/CO2/KH chart, how to measure it, or anything else, I'd recommend a simpler approach.

Get your tank set up. Start adding CO2. Start slowly. Gradually increase the CO2 rate over a period of several days until you see some change in the fishes behavior. Then back off a little. Go slow. Watch carefully. The change you're looking for isn't dead bodies at the filter inlet. Stressed fish will have rapid gill counts, will move up to the top of the tank, or will become lethargic. If you must, check the pH at the "stressed" level and then back off 0.2 points or so.

99% of people who tell you that you can acurately measure the ppm of CO2 in a home aquarium don't know what they're talking about. Measuring CO2 is actually a pretty tough thing to do.


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## dynafire (Dec 19, 2007)

Thanks for the reply. I will slowing increase my CO2 each day. I feed the co2 line into my return pump and there are ridiculously large amount of tiny bubbles. Is this a sufficient way of dissolving co2 or is there a better way to do it?


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## Zapins (Jul 28, 2004)

Better to buy or build a CO2 reactor and put it inline with the filter tube that returns water to the tank. You should get 100% dissolved gas.

http://www.aquaticplantcentral.com/forumapc/diy-aquarium-projects/2958-diy-inline-reactor-plans.html


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## dynafire (Dec 19, 2007)

Thanks for the suggestion Zapins. I just gathered all the supplies from Lowes today and will be building it tomorrow. I hope it works but I need to change it just a tiny bit. I guess I should be consulting the other thread for advice if I come to an obstacle. Btw how accurate is the drop checker for estimating the co2 level?


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## ray-the-pilot (May 14, 2008)

BryceM is 100% right about how to set the CO2 level in your tank. Just increase the level slowly and check out what your fish and plants do. I’d also suggest that you get a drop checker to help you gauge the level of CO2 in your tank.


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