# Adjusting pH, kH, and CO2 levels - Am I Overthinking This?



## jfynyson (Apr 15, 2013)

Long story short is no you cannot truly raise your alkalinity (KH) while lowering your pH. Think about the titration for KH. It's an acid and base titration (same goes for the drop checkers). The color changes with pH. KH is a measure of the alkalinity (base) and it wants to aid it keeping the pH up or buffering it from big swings in pH. CO2 in water makes carbonic acid thus lowering the pH. This is simply the nature of acid / base reactions so you're not going to lower your pH (make it more towards the acid side of neutral) while increasing your base (KH).


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## xmas_one (Feb 5, 2010)

You're overthinking things. KH and pH are two of the least important parameters in this hobby. Get your ferts straight, good co2, suitable lighting and you can grow anything.


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## MangyMoose77 (Feb 19, 2012)

xmas_one said:


> KH and pH are two of the least important parameters in this hobby.


xmas_one - Though I agree with the latter part of your statement, I cannot accept your quote above to be true. Plant and animal health on some part is definitely attributed to pH and/or kH. There is just simply no way that every plant (or animal for that matter) will perform perfectly in every possible kH and pH combination for multiple reasons. 

I just cannot buy into the Scott's fertilizer theory of aquarium maintenance: "Feed your tank! Feed it!" If certain water parameters are not where they should be, there is no way you are getting the best results out of your fertilizer and to you plants.

Can it really be as simple as making sure your CO2 is at 30ppm and measuring fert properly for everything else to fall into line perfectly?

jfynyson - You have confirmed my inner battle. I didn't think that it was possible, and apparently it is not. So with the kH I have I would need to get my pH down between 6.5 and 6.7 to achieve 30ppm CO2!

That's quite an extreme change from my source pH of 8.0. What do people in my situation typically find themselves doing?


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## Dantrasy (Sep 9, 2013)

Is only been 4 days since introducing Co2, right? I think you should just monitor for now. Are your plants pearling? Do they look healthy? Any fish? If you have discus I understand your concern. 

30ppm is the 'magic' number, but you can still achieve success if it's a bit off. 

Like you, all this ph, kh stuff used to bother me a lot. my tap water ph is high, around 8. In the end I got RODI unit. I measure tds now (keep it around 130-140) and add a little bi-carb soda for kh after each wc. For me that was problem solved. The plants are super healthy and pearl like crazy. I don't keep discus. 

btw, when are you doing you water tests? Someone correct me if I'm wrong, but they should be done a long time after the co2 has switched off (e.g. morning time). You shouldn't do water tests during photo/co2 time.


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## MangyMoose77 (Feb 19, 2012)

Plants started pearling yesterday, everything looks great right now, I'm just seriously concerned that my pH would have to be so low to achieve the desired CO2 levels. I was thinking I could change the kH to help with that, but it's not possible.

No I'm not keeping discus, just a small shoal of congo tetras (6) and a chubby pleco. I recently changed my congos' diet and they look incredible!


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## plantbrain (Dec 15, 2003)

Many over think this. 

Just measure the KH.
Then see what pH you need to target say 30 ppm, you might need more than this, but start at 30 ppm.

Add enough CO2 gas to drop the pH to that level, generally about 1.0 pH drop.
Use pH to adjust up/down from there.

A pH meter is very useful for this.

Watch carefully over the day cycle to see where the pH/CO2 goes.
Watch fish carefully and new plant growth.

Never adjust CO2 and then leave for the day, you can kill your fish easily that way.


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## MangyMoose77 (Feb 19, 2012)

Thanks for the pointers plantbrain! I think I am actually going to buy a new kH test kit tomorrow. The one I have was given to me and I'm starting to wonder just how old it may be.

I have been talking to my friend about this and he seems to think my water would have a higher kH by default. South Central PA has so much dolomitic limestone almost everyone in this area has hard water.

If this is true, maybe my goal is slightly more obtainable than I originally thought!


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## Canuck (Apr 30, 2009)

I'm not an expert but it won't stop me from voicing some of the conclusions I've come to (right or wrong)...

1. How important is pH in aquaria? Probably not very important for plant growing. One can easily find a large number of successful aquariums across the a fairly broad band of pH values and a large number of aquaria that fail miserably at the same pH values. Could somebody grow plants at a pH of 3? I strongly doubt it, but I'm excluding extremes. The plants we grow can deal with a lot more variablility than land plants. Think about the changes in environment from wet season to dry season, from submerged to emersed, from soft water during rainy season to hard water during dry. These conditions would develop flora well designed to withstand more chemical variability than most land plants.

2. I stopped thinking of pH as an element or factor a long time ago and began to consider it more of a product of the environment. That begs the question is the pH really important or is it the mix of elements and factors that produce that pH the important part. Think of it this way, if a lawn benefits from the addition of lime is this because the pH changed or because the lime (carbonate) was added? Would the lawn have benefited if sodium hydroxide had been used to increase pH?

Comments?


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## Zorfox (Jun 24, 2012)

MangyMoose77 said:


> I know that some plants would do better in certain pH levels than others, but I can't help but think there has to be an commonly accepted optimum pH for nutrient intake.


Yes, optimal PH varies among plant species. Is there an optimal PH? Obviously, that would depend on the species of plants being kept. Since most tanks contain a wide variety of species a ph of 6.5-7.5 would be considered optimal. PH does play a role in nutrient availability. Nutrients can become unavailable at extreme PH ranges, iron in particular. Hydroponic growers pay particular attention to PH for these reasons.

That said, altering PH in an aquarium can be time consuming and expensive. It's a never-ending battle trying to maintain an "optimal" PH for plant growth. In reality, the efforts required to optimize PH is not rewarded by commensurate growth or overall plant health. Typically, it's best to use what your have and direct efforts toward other things that will increase plant health on a more measurable level.


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## Diana (Jan 14, 2010)

Land plants vs water plants

They are different. Some of the concepts in land plants are valid under water, too. Some are not. Please do more research about each of these concepts, or ask and I can go into more detail.

Land plants are in a large landscape, planted in the soil. If that soil is wrong you need to do something about it, and this does not usually mean bring in the backhoe and scrape it all down a couple of feet and bring in good stuff. It means test the soil before you do stuff and then do the right things to improve that soil. The same chemistry goes on in an aquarium, or in a planter box, but you are setting up a small container, and can do it right, and keep working with it to keep it on track. If you need to get rid of the soil in an aquarium (or even a large planter box if the budget permits) you can. You do not have to work with something that is too hard to work with or does not do what you want it to.

pH: 
Aquarium- As long as it is in the right range, the exact value is not important. I use pH in the aquariums as sort of 'the canary in the coal mine'. As long as the pH is stable, then the other things are probably doing OK, too. If the pH starts going off then I know to check other things. Sure, some plants and some fish have a preferred range and it is best to keep them in that range. I do indeed try to stock fish according to their water chemistry preferences, and pH is one, but not the most important. I roughly divide fish into soft water (neutral to acidic pH) hard water (alkaline pH) and neutral, or middle of the road. The mineral content is more important than the pH. 
Land-In the garden, the best time to work on the soil pH is when you begin. Anything you do after the plants are in the ground is not going to be as effective. Long term solutions, applied through the years are important, too, but this is more of a maintenance thing. If you can set it up right at first, then keep it that way. If you cannot set it up right then it is always a fight to try to fix it. 

KH- 
Aquarium-Agree with the above. You cannot raise the KH and lower the pH. However, there may be something else in your water if the KH is only a couple of degrees, but the pH is in the mid or upper 7s. You might ask the water company if they add something. My tap water has a KH of around 4-5 degrees, but the water company adds sodium hydroxide to keep the pH in the upper 7s to low 8s. A few aquatic plants can use carbonate as a source of carbon, but they only do this when the CO2 is missing from the water. Nitrifying bacteria and some other microorganisms use carbonates as a source of carbon, and a low KH can cause them to grow slower. Fish do not care. 
Land- any source of carbonates that works in one place will do the same in the other. Sources of carbonate or bicarbonate can be added to either. Limestone in any of its forms, coral, oyster shell and materials like baking soda, potassium bicarbonate and other things will raise the KH in both soil and water. Some materials dissolve faster, so the effects are more immediate.

GH:
Aquarium- The test for calcium and magnesium. These are required minerals for both fish and plants. However, some fish and a few plants can take in too much of these minerals if the water has them, and can die. Almost all the plants we commonly grow in aquariums will handle a very wide range of GH and do just fine. 
Land- we do not normally test the combination. Separate tests for Ca, Mg and pretty much all the other fertilizers and minerals can be done for agricultural crops, but rarely done for ornamental. A basic soil test (N-P-K, pH) does not include these. 

CO2:
Aquarium- Sure is something to think about. 
Land- This is a concern in a well enclosed greenhouse. There are CO2 generators for this specialized purpose. 

Here is how I answer these concepts:

1) Test the tap water. GH, KH, pH, TDS. If I am making a blend (RO, rain or distilled + tap) then test that. 
2) Research the fish I want to keep. 
3) Alter the water in this order:
a) Set the GH where the fish want it. 
b) Set the KH about equal to the GH. 
c) Add peat moss if the fish are from a black water environment.
d) Ignore the pH as something I want to alter. Let the KH and peat (if any) set the pH to whatever is natural for it to do. THEN test it, and use it as I suggested above. If future testing shows a shift, try to figure out what else is happening. 
e) Usually the TDS will fall in line with what the fish prefer when the other things are right. 
4) If I am using a new substrate or decorations that I am not familiar with I might run a small tank for a couple of months and do some research. See if under my conditions the substrate, driftwood, rocks or whatever does what other people say it does.


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## MangyMoose77 (Feb 19, 2012)

Went to Pecto today to pick up a kH test kit. I can't believe I actually thought they would have one.....I will need to make the trip down to Lancaster to the mecca of all things aquariums, That Fish Place!!  My wife typically limits me to one visit per month. I can't imagine why!

I should have assumed that Diana would have chimed in here.  You make many great points about land vs. aquarium. 

As far as GH is concerned for land though, we typically don't test it separately because deficiencies can usually be supplemented through applying some sort of pelletized lime. The two most common Calcitic (Ca) and Dolomitic (Mg + Ca). 

The soil tests done through my place of work will test not only the pH but will also tell us what type of lime to supplement (calcitic or dolomitic). By default an area would usually lean toward one type of lime or the other. In South Central PA we typically apply dolomitic, in Southern Maine it's typically calcitic......but I digest...... 

Essentially on land you are changing GH and pH and at the same time when you are applying lime. We just don't use the vernacular 'GH'. It can also be noted that as a plot of land sits it will naturally acidify, so we are able to adjust pH and supplement Ca or Mg as needed. However, if someone applied lime of the wrong type e.g. calcitic to adjust pH but they are also deficient in Mg, there is no way to apply Mg by itself, so in the name of total plant health, you are forced to wait it out and supplement 6 or 12 months later. 

Would it perfect to start from the ground up (haha, it's funny because it's a pun!) and build a soil profile (or even an aquarium substrate profile) the right way the first time? Absolutely! However for those of us who started a tank and *then* decided to get serious and do it the 'right way', we become stuck with what we have or are forced to re-build from the bottom up. The same seems true about water chemistry. Fundamentally, we are sort of stuck with what the good Lord gave us by well or by city water.

Again, I'm no water chemist so it takes my brain a bit to shift from land to sea if you will, but I can appreciate the complexity of trying to get all of this right. Since I'm well versed in flipping turf and ornamentals from junk to healthy, it would be a great sense of pride to be able to do the same for my aquarium plants and fish. Moreover, I want prove to my saltwater friends that our freshwater tanks can be just as impressive, if not more!


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