# CO2 and PH Issues. Help!! I have a mess!



## Tex Gal (Nov 1, 2007)

I really need some help with CO2. I have been reading furiously and need answers. I started with a heavily planted tank. 3.08 watts/gal light, 125 g tank. Two Rena Xp3 filters and just got a pressurized CO2 system. My source water is 1.68 KH. I read the beginning article on the DFWAPC and found the KH/ph chart to determine CO2 tank levels. Found that chart in the PPS Pro system and on Rex Grigg's site. I tested my KH 1.68 and pH 7.0. Decided that I really had low KH according to charts to get 30ppm of CO2. I added baking soda to raise KH to 3 which sent pH to 7.2. My CO2 took pH back to 7.0 by next day. So I added more baking soda and raise KH to 6 which raised pH to 7.3. 

Now 1.5 days later pH has not reduced but gone up to 7.4. My CO2 is up as far as my reactor can handle. (Aqua Medic Reactor 1000) In the meantime Rex tells me that the chart really can’t be used this way because water usually has other buffering agents that come into play. According to the chart my KH would have to be at 10 to get my CO2 to 30ppm. Mine is at 6ppm and hasn’t gotten the pH down to 7.0 again. Rex also said that I should only raise my KH 2°, which is way lower than the chart or than I raised it. He says don't worry because CO2 changes of pH don't hurt the fish. He says they fish aren’t affected because the osmolarity of the water isn’t changed. Trying to understand this, I did a search on fish and pH. I found some info that basically says since the fish get saturated by the water they are in the pH they need needs to be close to the pH of their blood so that they can absorb O2. Perhaps this is all about osmolarity 

1.	Does everything go out the window when you use CO2 - recommended pH for certain fish doesn't matter anymore?
2.	If I can’t use the chart to figure out my CO2 what is it’s purpose?
3.	How do I measure my CO2? Do I need to get a drop measurer?
4.	Why measure for pH if the CO2 is changing it? How do I know how much change the CO2 is having on it and the osmolarity is changing?
5.	What do I do now? Should I do a water change to bring the pH down or just wait to see if the CO2 will eventually do it. 
6.	Do I have a bad reactor? It says it can treat up to 500 gallons. I only have 125 gallons.

I’m sorry for all the questions. It’s not that I don’t trust the articles but I need to understand the thinking behind all this or I will not be insulated from my misunderstanding of the information I am reading in all of these places.

Thanks for any help you all can give me. I have already read DFWAPC article for beginners, Rex Grigg’s site. Info at ThePlantedTank.com. I have also been reading previous threads where you have helped others.


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## hoppycalif (Apr 7, 2005)

Fish in nature live in certain types of water, hard water from the carbonate springs that feed the streams or lakes, soft water kept that way by the heavy layer of leaves and tree branches in the water, etc. But, our aquariums aren't natural. We all want to grow plants, or we wouldn't be here on this forum. So, we provide our aquariums with the conditions that help plants to grow well - light, good nutrient concentrations, and, for most of us, CO2 in abundance.

CO2 in water becomes carbonic acid, in part, which lowers the pH of the water. The pH depends on how much carbonate there is in the water, as measured by KH. But, it also depends on what other substances there are in the water, such as tannins and phosphates. The chart of pH, KH and CO2 is based on water containing only CO2 and carbonates - not what we typically have in our tank. So, the chart isn't at all accurate for typical aquarium water in a planted tank.

If you use a drop checker, using distilled or deionized water which has been adjusted to a known KH with carbonates, you can make that CO2, pH, KH chart work. The sticky in the DIY section explains how to do that.

Back to the fish: pH in natural waterways comes about due to various substances that are naturally in the water. The fish are sensitive to those natural substances and their concentrations, not to the pH itself. So, the recommendations that say a certain fish needs to be in 7.2 to 7.6 pH, for example, are not really valid in our aquariums. Many people keep and even breed fish in water with a pH far outside of those recommendations. It is far worse to add lots of substances to the water to try to adjust the pH to fit the recommendations, than it is to ignore the recommendations. Doing that means you are loading up the water with dissolved stuff, and fish are sensitive to that.

When you introduce new fish to the aquarium, just use a slow acclimation technique to get the new fish used to the new water gradually, and the variation from the recommendations will not be a problem. Of course you can't carry this idea too far - you can't keep brackish or salt water fish in a fresh water tank of low pH, low KH, low GH water. But, for almost all other fish this works.

I hope this is helpful and not oversimplified.


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## Tex Gal (Nov 1, 2007)

Thanks for the fish info. It makes sense, but I'm not sure where this leaves me. I began with what I thought was a balanced tank with a pH of 7. I have added hard solids (baking powder) to adjust my KH. I'm not sure I should have at this point but it's done. When I fertilize I will be adding more hard solids. I am adding CO2. I'm supposed to be checking for all fertilizer values once I do that. So what perimeters do I keep my pH at, do I worry that it is now 7.4. or do I just not consider the pH? I always checked pH because I understood that it was a check on values affected by plant decay, tank load, etc. I will still have those issues even though I am trying to grow plants and have CO2. 

I did read the sticky about the drop checker. Didn't thoroughly get it but will go over it until I do. Should I do a water change to get the baking soda back out?


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## hoppycalif (Apr 7, 2005)

Your tap water will be fine for both the fish and the plants. No good reason to add anything to it to change its parameters, with one exception. Plants need calcium and magnesium to grow well. If you have a GH that is very low, below 2 or 3 degrees of hardness, for example, or if you check your water company water quality report and find there is little or no magnesium in the water, it is good to add enough GH builder, either Equillibrium or Barr's GH Builder, to raise the GH a couple of degrees. I recommend that you do a big water change, about 50% or more, and just use the water as it is then.

For fertilizing, you can use the Estimative Index method (see the sticky in the Fertilizing Forum), and not worry about doing any testing for nutrient levels. That method is a good way to get started in growing plants, and many of us continue to use it for years. Get or make a drop checker, buy some 4 dKH distilled water from http://www.aquaticplantcentral.com/forumapc/sale-trade/37080-kh-standards.html, for example, and you can tell how much CO2 is in the water without measuring KH or pH of the tank water. These steps simplify the process a great deal.


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## Tex Gal (Nov 1, 2007)

Thanks hoppycalif. I will do a significant water change today. I'm sure my pH will go down. My GH is fine. I'm going to learn this no matter how long it takes me!

Does adding CO2 change the KH of your water?


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## hoppycalif (Apr 7, 2005)

Adding CO2 changes the pH of the water, and nothing else. KH is the ppm of carbonates in the water, and CO2 is not carbonates. (Actually, when we measure KH we are measuring the alkalinity of the water and not just the carbonates, but the same principle applies.)


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## Tex Gal (Nov 1, 2007)

Tonight I changed 50% of my water. At first the pH went up to 7.6. I assumed it was because I was also removing the CO2 that had been keeping it at 7.4. 1.5 hours later it has dropped to 7.5. I will have to do testing to see what my values are. Got some fertilizer at the LFS and hope to add a small amount until what I ordered from Rex Grigg arrives. Once I get things settled down I will try to put a px up. 

Thanks so much for helping me Hoppy. I really appreciate it. I am on the look out for a red sea drop checker. Already ordered the 4 dKH solution.


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