# Dosing baking soda as a CO2 substitute?



## Blue Ridge Reef (Feb 10, 2008)

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.


----------



## Grah the great (Jul 3, 2013)

Blue Ridge Reef said:


> 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.


----------



## minorhero (Mar 28, 2019)

Grah the great said:


> 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.


----------



## EdWiser (Jul 14, 2015)

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. [emoji3]


----------



## Grah the great (Jul 3, 2013)

EdWiser said:


> 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. [emoji3]



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.


----------



## CannaBrain (Oct 3, 2008)

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.


----------



## Blue Ridge Reef (Feb 10, 2008)

Not being a jerk here but there's really no experiment. The alkalinity of the tank's water will only rise.


----------



## Andy H (Nov 14, 2019)

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.


----------



## Ddrizzle (Jan 30, 2019)

Grah the great said:


> 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.


----------



## AbbeysDad (Apr 13, 2016)

If you have fish, the dramatic change(s) in pH could be a killer!


----------



## GrampsGrunge (Jun 18, 2012)

EdWiser said:


> 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. [emoji3]



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.


----------



## GrampsGrunge (Jun 18, 2012)

Grah the great said:


> 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.


----------



## Ddrizzle (Jan 30, 2019)

GrampsGrunge said:


> Grah the great said:
> 
> 
> > 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.
> ...


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.


----------



## Andy H (Nov 14, 2019)

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.


----------



## LuluCocoPopoRoro (Feb 20, 2019)

If you’re looking to increase co2, just increase surface agitation.

You can do this with a bubbler or poppy pipe.

People are going to say it will LOWER your co2, but in reality, if you’re not adding pressurized co2, then the co2 will go up from the gas exchange.


----------



## GrampsGrunge (Jun 18, 2012)

Active aeration of otherwise elevated CO2 levels in water _will always_ lower the CO2.


----------



## LuluCocoPopoRoro (Feb 20, 2019)

Key part is “otherwise elevated”. The gas exchange brings o2 and co2 to equilibrium. Unless your tank is crazy overstocked, or you’re adding co2 by other means, co2 will be added via gas exchange.

I was surprised when I heard this too, so I posted on a chemistry forum and asked there 

https://chemistry.stackexchange.com...tion/126795?noredirect=1#comment243364_126795


----------



## Ddrizzle (Jan 30, 2019)

LuluCocoPopoRoro said:


> Key part is “otherwise elevated”. The gas exchange brings o2 and co2 to equilibrium. Unless your tank is crazy overstocked, or you’re adding co2 by other means, co2 will be added via gas exchange.
> 
> I was surprised when I heard this too, so I posted on a chemistry forum and asked there
> 
> https://chemistry.stackexchange.com...tion/126795?noredirect=1#comment243364_126795


Well whatever "equal" is, is super low co2 because whenever I airate when my co2 is on, I need to crank it to keep it above dark blue.


----------



## LuluCocoPopoRoro (Feb 20, 2019)

Maybe I misunderstood stood the point of this point, but my understanding is that the op wanted to increase CO2 in the tank, without having to do pressurized co2.

If you’re pumping co2 into your tank, then surface agitation will probably lower your overall co2.

But If you’re like the op, and not pumping co2, then agitation will probably increase it.


----------



## Ddrizzle (Jan 30, 2019)

LuluCocoPopoRoro said:


> Maybe I misunderstood stood the point of this point, but my understanding is that the op wanted to increase CO2 in the tank, without having to do pressurized co2.
> 
> If you’re pumping co2 into your tank, then surface agitation will probably lower your overall co2.
> 
> But If you’re like the op, and not pumping co2, then agitation will probably increase it.


Yeah, and in an effort to help noobies who read this thread I'm trying to clarify that neither of those options are going to produce results similar to injecting co2. 

This is particularly important for dwarf baby tears and similar co2 hungry plants.


----------



## john borr (Oct 28, 2011)

You could put a teaspoon of baking soda in a soda bottle add warm water and a teaspoon of yeast that would get co2 to plants if you are OK with DIY methods.


----------



## Matt69 (Jul 9, 2017)

I don’t think you would have to dose carbonate daily, I think check it weekly and dose as needed. Essentially all your doing is a low tech tank selecting plants like Val and maintaining a KH at a slightly higher level maybe like 6. Let us know what plants you decide and how it works. 


Sent from my iPhone using Tapatalk


----------



## Grah the great (Jul 3, 2013)

This is quite a bit more info than I expected...thank you. I am experimenting with yeast CO2 on another tank currently, I was just wondering if there was any reasonable way to improve low tech growth.


----------



## cl3537 (Jan 28, 2019)

Grah the great said:


> 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?


No they wouldn't. If you are doing regular water changes (as you should) it will not change anything appreciably. The reference to plants using Carbonates is not interpreted correctly on most places on the internet. Walstad was describing a situation where no water changes are being performed and where plant density is very high. In most hobbyist tanks those two conditions don't exist and plants do not 'use' Carbonates at all and the CO2,kh, and pH remain stable due to water changes and open Water/Air/CO2 exchange.


----------



## Ddrizzle (Jan 30, 2019)

cl3537 said:


> Grah the great said:
> 
> 
> > 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?
> ...


Some plants do use bicarbonates or they convert bicarbonate to co2 themselves, both lowering bicarbonates in the water. Please see my post above as well as the chart in it.

Now to the point you're probably trying to get at - they are going to grow slow as hell if at all just on bicarbonates, if they can in the first place. It seems hard water plants are more adjusted to use bicarbonates either directly or indirectly according to the carbon chapter in Walstad's book.


----------



## cl3537 (Jan 28, 2019)

Ddrizzle said:


> Some plants do use bicarbonates or they convert bicarbonate to co2 themselves, both lowering bicarbonates in the water. Please see my post above as well as the chart in it.
> 
> Now to the point you're probably trying to get at - they are going to grow slow as hell if at all just on bicarbonates, if they can in the first place. It seems hard water plants are more adjusted to use bicarbonates either directly or indirectly according to the carbon chapter in Walstad's book.


Read page 97 in the same book and chapter you quoted.

1) Plants prefer CO2 10 to 1 over carbonates. (Even the low CO2 concentrations present in low tech tanks).
2) A limited number of plants (only a few in our hobby (Ludwigia Repens(?) except Valisneria Spiralis) have been proven to use bicarbonates directly and they won't likely do that under conditions of the standard Air/Water ~3ppm of CO2 present in most low plant mass open air system aquariums with a filter.

Most of our hobbyist plants are softwater species and prefer and thrive in lower kH environments, some can adapt to medium hardness of water but it is not ideal. 

If I had more time I would dig into the references in that chapter and determine the experimental conditions that those plants were under in order to prove bicarbonate uptake (references 12,23) and if the plants were growing in stagnant waters with poor CO2/O2/Water exchange or not.



LuluCocoPopoRoro said:


> Key part is “otherwise elevated”. The gas exchange brings o2 and co2 to equilibrium. Unless your tank is crazy overstocked, or you’re adding co2 by other means, co2 will be added via gas exchange.
> 
> I was surprised when I heard this too, so I posted on a chemistry forum and asked there
> 
> https://chemistry.stackexchange.com...tion/126795?noredirect=1#comment243364_126795


That discussion refers to extreme high atomspheric pressure or they made a mistake on the order of 10X to estimate CO2 in water concentrations. 0 - 5ppm is a more reasonable estimate of CO2 concentration in aquariums without artificial CO2 injection.


----------



## Ddrizzle (Jan 30, 2019)

cl3537 said:


> Ddrizzle said:
> 
> 
> > Some plants do use bicarbonates or they convert bicarbonate to co2 themselves, both lowering bicarbonates in the water. Please see my post above as well as the chart in it.
> ...


Yep, that's essentially what I said above. I tried to make it obvious that these are extreme circumstances


----------



## cl3537 (Jan 28, 2019)

Ddrizzle said:


> Yep, that's essentially what I said above. I tried to make it obvious that these are extreme circumstances


Those are not the conditions likely to be seen in the OPs tank and not in most tanks in this hobby unless they intend on doing a walstad with no filter or water changes.


----------



## burr740 (Feb 19, 2014)

Both sides of this surface agitation debate are somewhat correct. If you have a low tech aquarium - no injected co2 - your baseline co2 will generally be somewhere around 2-3 ppm, this can vary at different altitudes but its usually around that.

So there you are with your low tech aquarium and 2-3 ppm of co2 in the water. Plants can easily take that up. There might be zero in the water a couple hours after the lights come on, or say halfway through the photo period. (This is the reason behind doing a couple hour siesta mid-day with the lights off, to let the co2 level build up again. How effective it is is a different subject)

Having strong surface agitation will help maintain that baseline 2-3 ppm via increased gaseous exchange with the atmosphere. It will help 0 ppm become 2-3 ppm. But it will not turn 2-3 ppm into say 10 ppm, or even 5. 

The baseline is determined by pressure inside the tank vs outside. When the co2 level drops below the baseline, co2 from the atmosphere automatically tries to move into the water. Surface agitation speeds this up. 

If co2 is above the baseline level, as it is with injected co2, or perhaps after a water change when there's usually a couple extra ppm in the tap, co2 is automatically heading out of the water and into the atmosphere, aka degassing. Surface agitation speeds this up too. Whether its a high tech with 30 ppm or a low tech with 1, co2 levels are perpetually heading for the baseline.

Short answer: The more surface agitation the better in a low tech tank. 

Its good for high techs too, primarily for increasing O2 content, but it does require injecting more to compensate for the increased degassing. Not much more but a little more. Its generally worth the trade off to strike a happy medium. This is for high techs with injected co2. With low tech you can throw a paddle wheel boat in there and its only going to help matters.


----------



## DaveKS (Apr 2, 2019)

GrampsGrunge said:


> 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.
> ...


Yep, add some peat or leaves to tank/change water to add humic and fulvic acid compounds and many elements will increase their bioavailability to plants substantially. Fulvic acids will even deliver nutrients right through the cell wall tissues of plant without plant even having to expend any energy to obtain it. Small amounts will handle it, you don’t have to Blackwater your tank to get this benefit. Just a barely yellow tint is all you need.

RO and tap water is completely devoid of humic and fulvic acids, add them in yourself. They also protect your fish from water change shock and are a natural bacteria/fungicide. There is absolutely zero down side to adding them to your change/tank water, there is not a aquatic ecosystem on the face of planet that does not contain these compounds in some amount. If you’ve got lots of wood in your tank it will produce all you need of these compounds, if you stringently vacuum substrate and tank has no woods, just rock and sand you’ll have to add them. They are a natural byproduct of decomposition.


----------



## cl3537 (Jan 28, 2019)

burr740 said:


> So there you are with your low tech aquarium and 2-3 ppm of co2 in the water. Plants can easily take that up. There might be zero in the water a couple hours after the lights come on, or say halfway through the photo period.


Are you sure CO2 levels can go to 0 or even drop appreciably in small aquariums with filters?

Do you have any examples of high fluctuations in pH in low tech tanks ph 5 - ph 10?
I have yet to see an aquarium that has parameters like a stagnant swamp or a low alkalinity lake.
Do you see any aquariums that look like this?










Star Lake Vermont (referenced in walstad's book) as a low alkalinity lake.
It is theoretically possible, just not very likely in hobbyist tanks.


----------



## burr740 (Feb 19, 2014)

cl3537 said:


> Are you sure CO2 levels can go to 0 or even drop appreciably in small aquariums with filters?
> 
> Do you have any examples of high fluctuations in pH in low tech tanks ph 5 - ph 10?
> I have yet to see an aquarium that has parameters like a stagnant swamp or a low alkalinity lake.
> ...


Not sure I understand the question, or what PH or that pond in the picture has to do with It? Plant uptake can easily zero out 2-3 ppm of CO2 in an aquarium. Have I ever tested this personally with equipment sophisticated enough to read a ppm of CO2? No I havent


----------



## Asteroid (Jul 26, 2018)

cl3537 said:


> Are you sure CO2 levels can go to 0 or even drop appreciably in small aquariums with filters?


Isn't that the base reason that Walstad promoted the Siesta period for low-tech dirt tanks? Co2 that was built up overnight would be depleted during a full day light cycle. By doing the seista period it allowed co2 levels to be built up again. The exact decline or increase isn't really that important. What is important is that it made more co2 available.


----------



## Ddrizzle (Jan 30, 2019)

Asteroid said:


> cl3537 said:
> 
> 
> > Are you sure CO2 levels can go to 0 or even drop appreciably in small aquariums with filters?
> ...


Yes and the chart I posted above literally shows this and backs you up.


----------



## cl3537 (Jan 28, 2019)

Asteroid said:


> Isn't that the base reason that Walstad promoted the Siesta period for low-tech dirt tanks? Co2 that was built up overnight would be depleted during a full day light cycle. By doing the seista period it allowed co2 levels to be built up again. The exact decline or increase isn't really that important. What is important is that it made more co2 available.


First the siesta was not to my knowledge proven effective.
Second, Walstad isn't that dirted, no water changes, and even the filter is optional? (aka all Natural....)

Walstad can promote whatever she likes, it is up to us whether we beleive what she has written or extrapolated is applicable to the tanks we discuss here. I certainly don't in this case.

Bump:


burr740 said:


> Not sure I understand the question, or what PH or that pond in the picture has to do with It? Plant uptake can easily zero out 2-3 ppm of CO2 in an aquarium. Have I ever tested this personally with equipment sophisticated enough to read a ppm of CO2? No I havent


That was the example from Walstad's book of a low alkalinity lake, it happens to be chock full of algae, phytoplankton, and plants that can use CO2. This lake allows CO2 to go to practically zero (ph ~10) and great fluctuations in pH due to low kh. It is so different from the conditions in our tanks I can just about disregard any conclusions drawn from studies on this lake as being applicable for hobbyist purposes. 

It is my assertion that shallow(small) tanks never go to 0ppm CO2, there an equilibrium maintained with air CO2 concentration and thus the impact of Carbon uptake from Carbonates is negligible. I think this is an easy assertion with reasonable flow from a filter and surface mixing.

I still remember the debates with @Edward about pH decreasing 'dramatically' at night from all the CO2 plants were releasing. It has never happened to me or to him or anyone I spoke to who runs CO2 24/7. The same can be said about pH increasing dramatically during the day from depletion of CO2. I have never seen it in a hobbyist tank and would welcome someone with data who has.


----------



## cl3537 (Jan 28, 2019)

Ddrizzle said:


> 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.


Please stop misquoting Walstad's book, nothing reacts with Calcium, there is no redox chemistry going on in the water, there is no Calcium (which is a metal) in the water. 

The Calcium ions(Ca2+) present in water do not do any sort of reacting and they remain Ca2+ throughout. All Walstad was referring to was changes in pH can allow Bicarbonates which are soluble to precipate out as Calcium Carbonate (which is marginally soluble in neutral water) in more alkaline water.

You would be better off copy and pasting the whole paraphrah and citing the author rather than trying to sloppily paraphrase parts of her book, that leaves less room for misinterpretation.


----------



## burr740 (Feb 19, 2014)

cl3537 said:


> It is my assertion that shallow(small) tanks never go to 0ppm CO2, there an equilibrium maintained with air CO2 concentration and thus the impact of Carbon uptake from Carbonates is negligible. I think this is an easy assertion with reasonable flow from a filter and surface mixing..


This assertion is logical but it disregards plant uptake. That's what will take 2 ppm to zero because plants are using it faster than it can reabsorb from the atmosphere.



cl3537 said:


> I still remember the debates with @*Edward* about pH decreasing 'dramatically' at night from all the CO2 plants were releasing. It has never happened to me or to him or anyone I spoke to who runs CO2 24/7. The same can be said about pH increasing dramatically during the day from depletion of CO2. I have never seen it in a hobbyist tank and would welcome someone with data who has.


Plants do release some CO2 at night when they are in respiration mode but its a small amount compared to what they take in. I believe it is known as net carbon sink. And most studies on this involve terrestrial plants, where it varies a great deal according to the species type and also things like temperature. Hard to say to what degree it happens in our aquariums.

Ive never heard of a high tech's PH going up at night. Frankly it's not going to happen because there's a lot more in the water to degas than what the plants theoretically would release. If anything it would slow or reduce the rate of increase (PH) a little bit.

Now, it may drop at night if you run CO2 24/7. It amost certainly will. But that is mostly because the plants arent taking it in at night so naturally there will be more accumulating in the water. You could argue over how much is due to the plants releasing but it'd be hard to prove beyond saying it probably contributes a little bit 

I dont see how it could happen in a low tech because the plants dont have any extra to begin with. Its all being used to grow. And the ppm we're talking about are so low to begin with I dont see how it would be enough to even notice. But Ive never paid that much attention to a low tech so could be wrong. That is just what seems logical to me.


----------



## Asteroid (Jul 26, 2018)

cl3537 said:


> First the siesta was not to my knowledge proven effective.
> Second, Walstad isn't that dirted, no water changes, and even the filter is optional? (aka all Natural....)
> 
> Walstad can promote whatever she likes, it is up to us whether we beleive what she has written or extrapolated is applicable to the tanks we discuss here. I certainly don't in this case.


Not sure what you mean "Walstad isn't that dirted" did you mean "is dirted". So you don't believe in a dirted/soil tank that the substrate would build some co2, get used by the plants (if mass is high) and then the siesta would shut down plant uptake, the co2 would build again (above the normal 2-3 ppm) and the plants would have more available with lights on. I know Walstad states this she has repetitive tests of this. Easy enough to do.

With that said I see no benefit in a siesta in low-tech inert or obviously hi-tech. Why shut down plants that conditions exist for them to grow optimally.


----------



## KayakJimW (Aug 12, 2016)

Asteroid said:


> With that said I see no benefit in a siesta in low-tech inert or obviously hi-tech. Why shut down plants that conditions exist for them to grow optimally.


When I first heard of putting a break in the photoperiod (decades ago), the idea was marketed toward fixing algae issues. The idea being that algae was a simpler life form that thrived from lots of light. Plants are more complex and able to snap to it and grow quicker so the siesta was to help plants out-compete the algae. Mind you this was chatter between a few guys at LFS's and got repeated, etc like so much advice in our hobby, probably no experiments run or fact checking, or even much anecdotal evidence, just a concept that got accepted and repeated. Sold as an algae bandaid. That's how *I* first heard about it anyway... But yeah, the biggest/ only? benefit I see from a siesta would be the owner's viewing pleasure, ie. tank takes a nap while you're at work, to maximize before and after work viewing with lights on. Neat concept for dirt/ Walstad style tanks tho...


----------



## cl3537 (Jan 28, 2019)

Asteroid said:


> Not sure what you mean "Walstad isn't that dirted" did you mean "is dirted". So you don't believe in a dirted/soil tank that the substrate would build some co2, get used by the plants (if mass is high) and then the siesta would shut down plant uptake, the co2 would build again (above the normal 2-3 ppm) and the plants would have more available with lights on. I know Walstad states this she has repetitive tests of this. Easy enough to do.
> 
> With that said I see no benefit in a siesta in low-tech inert or obviously hi-tech. Why shut down plants that conditions exist for them to grow optimally.


I meant, Walstad tanks have soil substrate and are designed to be no maintenance much like a natural lake or pond. That is not what the OP is considering here.

I had a tank without a filter 30 years ago, in biology lab, it smelled awful, had snails all over the place, high density of overgrown but healthy plants and fish. When I think of Walstad I think of that tank. But that seems a far cry from what the OP was doing here.



burr740 said:


> This assertion is logical but it disregards plant uptake. That's what will take 2 ppm to zero because plants are using it faster than it can reabsorb from the atmosphere.


I am not questioning plant absorption and release of CO2 during the photosynthesis cycle, that is not in dispute.

However the affinity of water for CO2 as you approach 0 ppm CO2 in the water would be very high. The concentration of CO2 in the air is much more than that in the water and if there was near zero in the water that would drive the Air/Water/CO2 equilibrium to dissolve more CO2 into the water. With an open top tank and reasonable flow you would need a lot of fast growing plants to overcome that gas exchange equilibrium. These are conditions unlikely in a low tech hobbyist tank with a filter and reasonable surface gas exchange.

Bump:


burr740 said:


> Now, it may drop at night if you run CO2 24/7. It amost certainly will. But that is mostly because the plants arent taking it in at night so naturally there will be more accumulating in the water. You could argue over how much is due to the plants releasing but it'd be hard to prove beyond saying it probably contributes a little bit


No it doesn't, I run CO2 24/7 and so does @Edward, and the fluctuations in pH in both of our tanks are negligible from day to night. You are underestimating the Air/Gas CO2 equilbrium which is maintained. I have enough off gassing and CO2 absorption from AIR in equilbirum that what the plants may absorb or release is negligible. My tank is only a 17G so it has better gas and surface mixing exchange than deeper tanks, but I beleive Edward's is much larger than mine.


----------



## burr740 (Feb 19, 2014)

Well I can tel you 100% that PH does drop further at night if you leave the co2 running. Ive done it, both intentionally testing the waters for running it 24/7 and also from leaving it on by accident. Im not saying it will absolutely happen the same way in every tank. Of course it wont be the same. But your assertion that it wont happen period is wrong.

Idk about you but Edward I believe operates with pretty low levels of CO2 compared to what most high tech folks use. That probably has a lot to do with his observations.

Also things like surface agitation, or lack thereof, surface area + tank depth, how many plants and what kind, temperature, lots of variables are going to influence what happens.

Adding: Its an easy theory to test. Just leave the co2 running all night and see if the PH hasnt dropped another tenth or so by 3 am. Its not going to drop a whole point or anything. But that extra tenth can be 10-15 more ppm depending on how much you started with. I would also hazard a guess that most folks arent paying close enough attention or dont have the right tool to accurately notice an extra .1 or .05 drop. We arent talking about a huge drop. That drop has already happened. You're starting from an already low point from saturation, and the lower it goes from there the more each little increment means in ppm. So even a .05 drop is significant.


----------

