Dosing baking soda as a CO2 substitute? - The Planted Tank Forum
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post #1 of 42 (permalink) Old 03-20-2020, 06:39 PM Thread Starter
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Dosing baking soda as a CO2 substitute?

Hi everyone! I understand that many aquatic plants can use carbonates as a substitute to CO2...so, in a low tech tank that was already hard and alkaline, would plants benefit if small amounts of baking soda (NaCO3, or Sodium bicarbonate) were dosed daily? I was thinking of dosing 1/8th to 1/4th a teaspoon per five gallons over the course of the week, which would add 3.25-6.53 ppm carbonate a day. If done in small doses every day, this shouldn't change the KH rapidly enough to harm livestock. Thanks
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post #2 of 42 (permalink) Old 03-20-2020, 06:46 PM
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Goodness if it were that easy, we wouldn't be setting up all these CO2 systems! Unfortunately sodium bicarbonate contains no carbon dioxide and will only raise your KH and pH. With citric acid mixing, you can DIY a CO2 system employing baking soda though.
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post #3 of 42 (permalink) Old 03-20-2020, 06:53 PM Thread Starter
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Goodness if it were that easy, we wouldn't be setting up all these CO2 systems! Unfortunately sodium bicarbonate contains no carbon dioxide and will only raise your KH and pH. With citric acid mixing, you can DIY a CO2 system employing baking soda though.

I know it does not have any CO2, per say...however, many (not all) aquatic plants can use carbonates (HCO3) as a substitute for CO2, and carbonates are abundant in baking soda. It's not the same as CO2 by any means...I was just wondering whether dosing modest quantities of baking soda would improve growth in plants in low tech tanks that can use carbonates.
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Originally Posted by Grah the great View Post
I know it does not have any CO2, per say...however, many (not all) aquatic plants can use carbonates (HCO3) as a substitute for CO2, and carbonates are abundant in baking soda. It's not the same as CO2 by any means...I was just wondering whether dosing modest quantities of baking soda would improve growth in plants in low tech tanks that can use carbonates.
I honestly have no idea. But before you do it to your main aquarium I would do a test case in a jar. Have a control jar you use normal ferts on etc and your test jar where you dose like you would if you were dosing your aquarium. See if your chosen plant lives or dies, or any significant change compared to your control.

A lot of plants won't do well in high KH water so even if your plants are using something from the baking soda.... you might kill them anyway. If you go the experiment route please post it! We always need more information on planted tanks.
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post #5 of 42 (permalink) Old 03-20-2020, 07:25 PM
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Plants like a low KH so doing this will raise the level to higher than plants like.
It is the carbon that the plants use. Not calcium. Corals use calcium.
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post #6 of 42 (permalink) Old 03-20-2020, 09:51 PM Thread Starter
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Originally Posted by EdWiser View Post
Plants like a low KH so doing this will raise the level to higher than plants like.
It is the carbon that the plants use. Not calcium. Corals use calcium.

Baking soda, NaHCO3 or sodium bicarbonate, has no calcium and thus does not affect GH at all...I think you are thinking of calcium carbonate (which is almost insoluble in water). Even adding a quarter teaspoon of baking soda over the course of the week would only add 2.6 degrees (or just over 43 ppm) carbonate hardness, or KH...assuming one does not slack on water changes, that isn't an unreasonable amount to add to a tank over the course of a week.
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post #7 of 42 (permalink) Old 03-20-2020, 10:34 PM
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I say give it a shot and test'er out, maybe in a tank w/ out livestock?

if you had the time/space/desire, might be interesting to make 2 identical tanks w/ relatively hardy and fast-growing plants, same light/substrate, then dose one w/ baking soda, one w/ out.

keep us updated if you give it a go. best of luck.
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post #8 of 42 (permalink) Old 03-20-2020, 11:48 PM
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Not being a jerk here but there's really no experiment. The alkalinity of the tank's water will only rise.
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post #9 of 42 (permalink) Old 03-22-2020, 01:49 AM
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Some plants can use alternative carbon sources. I have kept amazon swords and jungle val in moderately hard alkaline water with no problem. You could use use sphagnum peat moss in the filter or driftwood in the tank to combat the rise in alkalinity and pH you will see from dosing. Good luck.
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post #10 of 42 (permalink) Old 03-22-2020, 05:35 AM
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Quote:
Originally Posted by Grah the great View Post
Hi everyone! I understand that many aquatic plants can use carbonates as a substitute to CO2...so, in a low tech tank that was already hard and alkaline, would plants benefit if small amounts of baking soda (NaCO3, or Sodium bicarbonate) were dosed daily? I was thinking of dosing 1/8th to 1/4th a teaspoon per five gallons over the course of the week, which would add 3.25-6.53 ppm carbonate a day. If done in small doses every day, this shouldn't change the KH rapidly enough to harm livestock. Thanks :-)
To state that kh/bicarbonates are a fertilizer like co2 is, is inaccurate at best. However, if you have absolutely no carbon in your tank (zero kh and zero co2), your plants won't grow. Please read all of my edits below.
--------

I dont know if I i can find proof that this wont work, but what I'll say is that kh (and therefore carbonates) in no way make plants grow as fast as co2.

If that were the case simply having a kh above 0 would help them grow fast.

Edit: I'm reading the chapter on Carbon in Walstad's "Ecology of the planted aquarium" now. At first, it seems to be fundamental that co2 is what plants need, and bicarbonate and carbonates are not it. You can lower the ph to turn the bicarbonates into co2, where 8.5 ph is half co2 and half bicarbonates.

However, the next page talks about how seaweed etc in saltwater grows much faster than the fastest growing freshwater plant. The hypothesis is that seawater plants have adapted to leverage the massive amounts of bicarbonates (salt) in sea water.

So from what I can gather, the only way bicarbonates can substitute for co2 in freshwater plants is if the specific plant can do it.

Again, if this was normal then we wouldnt be dosing co2 into our tanks and kh would be magic.

Edit 2: I've attached a table from the book so that you can see just how low photosynthesis becomes when the plants are limited to bicarbonates instead of co2. DIC = all forms of carbon in the water, total.

Assuming other factors are nearly the same, it's a difference of 5.33x when comparing 10 am (co2 @ 76%) to 2 pm (co2 @ 2%).

Edit 3: Ah, there is a complete section on co2 vs bicarbonate uptake. Essentially, even the hardest water plants (meaning they expect kh/bicarbonates in the water) grow at least twice as fast when given appropriate amounts of co2.

In general, it says freshwater plants prefer co2 to bicarbonates 10 to 1, possibly because bicarbonate use takes up more energy. Freshwater plants leverage bicarbonates less effectively than even algae.

As a final note, some plants have gone as far to avoid using bicarbonates directly by making the immediate area a lower ph (around 6) so that the bicarbonate reacts with calcium in the water to form co2 for the leaves to absorb. Obviously in this case, co2 would be more efficient for the plants. A plant that does this is Potamogeton lucens.
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post #11 of 42 (permalink) Old 03-22-2020, 02:58 PM
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If you have fish, the dramatic change(s) in pH could be a killer!

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post #12 of 42 (permalink) Old 03-22-2020, 03:19 PM
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Quote:
Originally Posted by EdWiser View Post
Plants like a low KH so doing this will raise the level to higher than plants like.
It is the carbon that the plants use. Not calcium. Corals use calcium.

This is not true, plants do use calcium. It can be considered a minor macro nutrient.


Plants don't have much use for Na or Sodium and with boosting Sodium in a tank you're just adding a nutrient not much in demand of freshwater plants, and raising the KH needlessly.
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post #13 of 42 (permalink) Old 03-22-2020, 03:31 PM
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Originally Posted by Grah the great View Post
Baking soda, NaHCO3 or sodium bicarbonate, has no calcium and thus does not affect GH at all...I think you are thinking of calcium carbonate (which is almost insoluble in water). Even adding a quarter teaspoon of baking soda over the course of the week would only add 2.6 degrees (or just over 43 ppm) carbonate hardness, or KH...assuming one does not slack on water changes, that isn't an unreasonable amount to add to a tank over the course of a week.

Calcium Carbonate is not 'almost insoluble', it can vary in solubility depending on the level of Carbonic acid present in the water.


A quarter teaspoonful of food grade CaCO3 powder will appear to not dissolve in water immediately but if there's enough dissolved CO2 in the water it will dissolve within a day or mores time.


The good thing about CACO3 is that it raises both the GH and KH per volume of solid and it isn't as strong an alkaline per weight as Sodium Bicarbonate. It's also a slower change to the pH.
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post #14 of 42 (permalink) Old 03-22-2020, 07:17 PM
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Quote:
Originally Posted by Grah the great View Post
Baking soda, NaHCO3 or sodium bicarbonate, has no calcium and thus does not affect GH at all...I think you are thinking of calcium carbonate (which is almost insoluble in water). Even adding a quarter teaspoon of baking soda over the course of the week would only add 2.6 degrees (or just over 43 ppm) carbonate hardness, or KH...assuming one does not slack on water changes, that isn't an unreasonable amount to add to a tank over the course of a week.

Calcium Carbonate is not 'almost insoluble', it can vary in solubility depending on the level of Carbonic acid present in the water.


A quarter teaspoonful of food grade CaCO3 powder will appear to not dissolve in water immediately but if there's enough dissolved CO2 in the water it will dissolve within a day or mores time.


The good thing about CACO3 is that it raises both the GH and KH per volume of solid and it isn't as strong an alkaline per weight as Sodium Bicarbonate. It's also a slower change to the pH.
This is because the lower the ph, the higher the co2 content. 8.5 ph is 50% co2 and 50% bicarbonates. The lower the ph goes, the higher the co2 is.

So with that rule in place, of course adding bicarbonates will raise the kh and ph.

And the rate at which bamingnsoda dissolves is just a factor of it within itself. Potassium bicarbonate dissolves right away. It's what's in efervescent tablets.
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post #15 of 42 (permalink) Old 03-23-2020, 08:40 AM
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I think CaCO3 and MgCO3 found in lime. There are easily sourced limes and dolomites available on Amazon for use as soil amendments. These would be more useful sources of carbonate. They are both very common as parent material in soils around the world. Calcium and magnesium are secondary macro nutrients vital to plant health and growth.

You could use a lime powder if you want the most soluble form. Look on Amazon for lime powder used in gardening as an amendment. All lime has CaCO3 and MgCO3 in it. If you want to use the most soluble type of lime find a product with as little MgCO3 as you can possible. The CaCO3 portion of lime is more soluble than the MGCO3 portion. Although, what could happen is the Ca:Mg ratio will be over 10:1. All lime products are required to disclose the percentages of Ca, Mg, CaCO3, and MgCO3 on the label sometime you will also find CaO and MgO. I take the Ca and CaCO3 percentages and average them. Then I do the same with the Mg and MgCO3. Finally, divide both averages by the Mg and MgCO3 average. This will give you a ratio where Mg is one and will give you a easy to read Ca:Mg ratio. If you can't find a product that has a acceptable ratio buy two types and mix them. This is what I have done in the past when adding lime and dolomite to my filter or substrate. There are different theories concerning nutrient ratios, what they are, and their relevance to plant growth and health. Some people (a lot of gardeners, farmers, and agriculture researchers, but, also planted tank keepers) believe in ratios especially concerning Ca and Mg when growing plants. Lots of money and research are invested in the understanding of farming management and best fertilization practices, that support the importance nutrient ratios.

Another way to think about the type the lime you use is with these ratios in mind. Anywhere between 6:1 to 10:1, Ca:Mg will put you in the range of what I have used, others talk about having used, and what is currently understood to be appropriate.

If you have a substrate with a descent cation exchange capacity it will help keep the GH of your tank from rising if there are open exchange sites. Plants, fish, and inverts also use calcium and magnesium vital to their health. A possibility depending on the type of substrate you use is that the lime powder settles before it dissolves. Settled on the substrate it can react with acids produced from the breakdown of plant detritus, fish food, and dead bacteria to produce CO2.

You could also use pelletized lime which is lime powder pressed into small pellets for easier application. It would settle faster and also dissolve in a week or two.

There is also granulated lime that takes longer to dissolve but would be easier to use because it will not change Ca and Mg levels as fast but would provide an alternative carbon source for plants that can utilize it.

You seem to have knowledge of pertinent parameters so I will not explain how lime will change them and to what extent. Obviously how parameters change depends on the type of lime used.
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