PH 7.0 for a planted, freshwater aquarium?

[LabTest57]

I've been using Neutral Regulator, which is a phosphate buffer, to buffer my PH at 7.0; however, I've also just planted a few plants (natural) in my aquarium and my PH seems to be dropping really fast. I know it's the phosphates being depleted by the plants, so I began adding baking soda (sodium bicarbonate) to reach 120 ppm - aquarists have told me that that's the right amount of bicarbonates that should be present in order to keep my PH from dropping below 7.0 (even if it's a little bit higher than 7.0). I was wondering if by any chance there would be an alternate buffering agent that can be used for freshwater planted aquariums?

Now, that my PH is usually on the high side (between 7.4 and 7.8), I've been thinking that I should even add more plants. Why? Because, plants remove CO2 from the water and release oxygen, thus, increasing the PH of the aquarium. Since at night, they would release CO2, I was thinking of just keeping the bicarbonates at 80 ppm to ensure that the PH doesn't drop too quickly either. Any advice would be appreciated...

[Tech Support DD]

Generally, people with planted tanks choose to not use phosphate-based buffers, as excess phosphate levels may lead to algae issues. Since you now have plants in your aquarium, we recommend using our Acid Buffer and our Alkaline Buffer. These are non-phosphate based buffers that allow you to use these two
products in conjunction with one another in order to target a specific pH.

[LabTest57]

I don't see any difference between baking soda and alkaline buffer? They're both sodium bicarbonate, which buffers PH to around 8.0. If they are different, can you specifically (technically) tell my how/why?


Another thing, I was thinking I should just use Neutral Regulator, because it increases plant growth (plants need phosphorous) and will buffer my ph to around 7.2. However, I may need to add a lot of it, most likely once every week, but I can live with that.

[Tech Support JS]

Alkaline Buffer is a proprietary blend of bicarbonate salt and differs in composition as well as purity. Feel free to use Neutral Regulator if you want to in your planted tank, we just do not recommend it due to the various issues that can be caused by it and that it isn't a recommended buffer for planted tanks. If you want to try it out and see if you could come up with a balanced schedule, that sounds like a great plan for you.

[LabTest57]

When you said, "Alkaline Buffer is a proprietary blend of bicarbonate salt", you mean: Calcium bicarbonate, Potassium bicarbonate, Sodium bicarbonate, magnesium bicarbonate, hydrogen carbonate,etc.?

[Tech Support JS]

As I said, that is proprietary information; regardless, the salt in the complex has little to do with the point of the product, which would be to add carbonates/bicarbonates into the aquarium. The salt will not affect the pH and is simply a carrier salt. Thanks again for posting!

[LabTest57]

So, why does it state that I must still use Neutral Regulator with alkaline buffer (if not, acid buffer - to lower the ph at the same time) to target a ph? What are the bicarbonate salts present in that product that buffers the PH between 7.1 and 7.5? I'm sure there's no real blend, because if I have to use an acid buffer or Neutral regulator as well (to keep the ph from rising too much - which is why you need to use both products to target a PH), then it's like adding sodium bicarbonate to raise the PH and acid to target it [ e.g. sodium bicarbonate @ 70 ppm and below will buffer PH between 7.0 and 7.6 (that's if you inlcude the biological stuff that produces acids to keep the ph from going higher than 7.6), because @ 6.8 and below it just converts to carbonic acid. Then, adding dry acid to regulate the PH]; so, why not just use Neutral Regulator for everything? Because, In the end, for a planted aquarium, the phosphates in the water will deplete over time and the PH will rise/fall from the "blend" of bicarbonates in the water or the acids being produced by bacterial waste, fish waste, decaying food,etc.. I also know that aerobic bacteria use up very small amounts of bicarbonates, and plants will use it as a carbon source as well. So, why not have a buffer that comes already pre-mixed with other buffers in a big container?

I'm sorry to make this so complicated, but that's the issue I'm stuck with right now - I don't want keep making the same mistake over and over (e.g. I'd rather keep sodium bicarbonate @ 60 ppm in my tank and use dry acid or Neutral Regulator in small quantaties to regulate the PH, instead of buying and adding "crap" that I don't even know how/what the product realy is/does,etc.)

[Tech Support JS]

We do not recommend or state using Neutral Regulator with Acid or Alkaline Buffer, as they work in two different buffer systems. As you may or may not know, Neutral Regulator is phosphate based and Acid and Alkaline Buffers are carbonate based. For your situation, first decide which buffering system to use:

If you would like to use a carbonate based buffer system, use Acid and Alkaline Buffer to regulate the pH. The two work hand in hand by simultaneously adding the buffer system you need (Alkaline Buffer) while keeping your pH in check (Acid Buffer). If you notice the dosing charts listed, you will see that you use significantly more Alkaline Buffer than you do Acid Buffer. That is because the Alkaline Buffer will directly add the bicarbonates in your system and allow the Acid Buffer to fine tune your pH by gassing off a specific amount of the carbonates/bicarbonates (as CO2 gas). Carbonates and Bicarbonates have certain "pKa's" to which they want to buffer the pH. Chemically, your tank will want to have a pH equal to the pKa of Alkaline Buffer; the amount of carbonates/bicarbonates you have in your tank will determine how close your water pH is to the pKa of the buffer (which is high).

If you would like to use a phosphate based buffer, you can use our Neutral Regulator alone or in conjunction with Acid or Alkaline Regulator. These products work by blending certain pKA's of the different forms of the phosphate buffer. By blending Neutral Regulator with Acid or Alkaline Regulator, you will be able to target a certain pH.

Lets take a step back from chemistry and look at it a different way, say, using colors:

We will use Red for a carbonate based buffer system (the darker red your water is, the higher the pH is). In this scenario, you want a rosy pink tank. Alkaline Buffer will want to make your water very dark red; using Acid Buffer will remove some of the red caused by the Alkaline Buffer and allow the tank to become lighter and lighter red until you hit your rosy pink color. This is not a blending, but a fine tuning of concentration.

We will use Yellow and Blue for a phosphate based buffer system (you want your water a nice green color). One form of the phosphate will want to turn your water yellow, and the other will want to turn your water blue. Mixing them together will give you your green color. This is fine tuning by blending colors (pKa's).

In theory it would be nice to have a non-phosphate based buffer that can come pre packaged to give you a desired certain pH but it is not possible for several reasons. If you were to throw two inorganic buffers (such as Acid and Alkaline Buffer) into a bottle, you would have a truckfull of exploding bottles (though, the pH of the discharge would be neutral). Remember, these work by producing a gaseous byproduct. That would force us to use at least one, if not both, of the reagents as an organic buffer. Having looked into this, we have found that it works efficiently but produces algae and bacteria that consume oxygen in the water and resulted in fish death. It is not currently feasible do yet, and the current method is not all too difficult.

[LabTest57]

This is the information I was looking for, but isn't acid buffer the same as dry acid, and alkaline buffer has the same pKa value as sodium bicarbonate - which is 10.2?

I think it's cheaper to use baking soda and dry acid, and just use a specific dosing calculator (I use The Pool Calculator @ www.poolcalculator.com) or dosing method. I usually find out how to make the proper doses and adjustments through trial-and-error, but I've never had an imbalance in PH in my aquarium, because I do these experiments in a seperate tank w/ zebra danios (zebras danios are like lab rats - I'm not being cruel as they are very hardy fish, and wikipedia states that as well).

In a forum site about water chemistry, I've asked several questions about bicarbonates and PH (note: some examples were based on swimming pool scenarios,etc.) and these were the replies I got back:

The pKa for Carbonic Acid to Bicarbonate Ion is 6.3 while the pKa for Bicarbonate Ion to Carbonate Ion is 10.2 so I don't know where you are getting your "8,9 and 10" from. Though a pH buffer is strongest when the pH is near its pKa, there is no need to keep the pH there. You can still get significant buffering being roughly nearby and a pH of 7.5 isn't that far from the pKa of 6.3 so there is still significant buffering.

My comments about having a low TA to keep the pH from rising has nothing at all to do with the pKa. It has to do with the fact that the carbonate buffer system in water has dissolved carbon dioxide and that this outgasses from the water because the water is intentionally over-carbonated. The equilibrium amount of TA in water at a pH of 7.5 given the amount of carbon dioxide in the air is only 9 ppm (if CYA is 0 ppm). A higher TA has the water contain more dissolved carbon dioxide than in the air and when this outgasses, it causes the pH of the water to rise (and the TA to remain unchanged for technical reasons I won't get into here).

The TA only lowers when you add acid to lower the pH back down. Acid lowers both pH and TA. So the net effect of carbon dioxide outgassing and acid addition is a lowering of TA. One can intentionally lower the TA faster by lowering the pH and aerating the water since both of these (i.e. lowering pH and aerating) makes the carbon dioxide outgas even faster.

You can have almost any TA that you want and any pH that you want. If the pH is further away from the pKa, then there is less buffering, and if the TA is lower, there is less buffering, but there is still SOME buffering. Even 50 ppm is better than lower values.

As a specific example, with a CYA of 30 ppm, let's compare a TA of 100 ppm with 50 ppm. If I add 1 cup of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 10,000 gallons then with a TA of 100 ppm and starting pH of 7.5 I end up with a pH of 7.33 and TA of 96.9 ppm. If I instead start with a TA of 50 ppm, then I end up with 7.22 and a TA of 46.9 ppm. Notice that the amount the TA drops depends only on the amount of acid that is added, but the amount the pH drops depends on the TA level.

Generally speaking, if you aren't using acidic sources of chemicals, like Trichlor or Dichlor (accounting for chlorine usage), then you can use a far lower TA level. You may need to have a higher CH to keep the saturation index near zero.

[Tech Support JS]

This is getting off topic from the initial question, "PH 7.0 for a planted, freshwater aquarium?"--this technical jargon is getting us nowhere. Pool chemistry is not the same as aquarium chemistry (moreover, no two aquariums are even the same) and cannot be used in an analogous comparison. Do not compare the two water chemistries. Your examples are all for pool chemistry, and although they shouldn't be compared, you can still come away with basic chemistry information: buffering capacity is best when pH=pKa, but you will still buffer when you are not equal.

Feel free to brew up your own personal dosing regime, and for your knowledge, at STP, a 0.1M aqueous solution of NaHCO3 will yield a pH of 8.3 (information verified from speck sheet (Sigma-Aldrich) for CAS Number 144-55-8).

[LabTest57]

I know your only tech support to provide information, instructions, and advice for your company's products, and how to use them in an aquarium. However, this is how future products and methods are able to become available to solving water chemistry problems like the ones in this discussion. Pool chemistry and aquarium chemistry are both related to water chemistry and you can extract information from each other and comapre the variables,etc., so you can find out how to solve other problems.

I'm not a chemist and your only certified for seachem tech support,etc. So, the topic isn't off-topic as we're still trying to figure out a solution for 7.0 ph in a planted freshwater aquarium. You can ignore chlorine, CYA, borates, etc. as that will harm plants and fish, but the way bicarbonates and PH work in pool water is the same for aquarium water, as they both contain acidic and alkaline sources (e.g. fish waste, rain water (acidic) that can affect both pools and ponds, the fill water - which can contain bicarbonates and different PH,etc,), but the only difference is the surface area of the body of water and surface agitation by filters, pumps,etc. - this affects the CO2 concentration in the water,etc.

I will keep the topic updated when I come across new information that others can use for similar aquarium chemistry problems...

[Tech Support JS]

We do try to offer any aquarium related assistance, not just our products; I do have a degree in chemistry (as well as biology), so my knowledge of this topic isn't specific to Seachem's products. Forum posts are meant for open discussion, but to my knowledge we have covered the best, most user friendly solution of keeping the pH at 7.0 in a planted (or nonplanted) aquarium.

Although water body size is significant, there are many more significant differences than surface area when comparing the two chemistries. Much like chinese food and italian food are both types of food, deliver nutrients to the body, make you full, etc, but they are vastly different. I would not suggest comparing pool chemistry with aquarium chemistry. Yes, the bicarbonates will chemically react and proton donation/release will the same, but in the entire chemical symphony of a pool there are vastly different parameters. For instance, you cannot compare acid influxes in pools and aquariums by comparing rainwater into a pool and biological waste from fish in an aquarium; organic acids produced by fish are constant, organic, and fairly weak. Acid rain (typically consisting of Sulfuric Acid or Nitric Acid) in inorganic, stronger, and comes sporadically and in large amounts at once. That is one of the many points I could make in differing the two.

Any buffer system will have its faults, and we have a team of chemists working daily on developing/improving products.

[LabTest57]

Thanks for all your help, even though I may have made things complicated, but I guess the discussion ends here.

For my PH 7.0 solution, I decided to go with baking soda and dry acid, but over at a pool chemistry forum I found someone who can calculate the PH rise/fall and determine when and why it rises/falls using a model/application based on certain parameters: surface area, how much water is being pumped (this includes aeration,etc.,), Total Alkalinity or KH, Total hardness or GH (calcium hardness is the most common), the PH of the water,etc.

[Tech Support JS]

Im glad to hear you found a method that works for your tank, since ultimately that is what is important and each individual tank is different. Thanks for posting and have a great day!