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Discussion Starter · #1 ·
I know we provide plants CO2 when we give them high light and fertiliser conditions....
How does nature do this? I'm sure not too many healthy water pockets are CO2 rich. So I would assume the more CO2/light a plant likes, the less fully aquatic it is. I.e. it would be getting light and gas exchange from the air, or through minimal water layers.


We know many of these plants do well, planted above water, but with some water cascading over or by it, I guess because of less filtering of light and better gas exchange along with not loosing valuable moisture.


Now I understand the concept of bubble wands and surface agitation in general releasing CO2 from the water body into the atmosphere. But what if you had a tank with a Single plant (I.e. you are not concerned with the average CO2 levels in the tank), but at the base of the plant you had a bubble wand or ring blowing bubbles through the plant 24/7.


This is just academic, but does anybody else feel there is a chance that such a plant would grow better than say if the bubble wand was just sitting in a corner off-gassing the whole tank?


I am just trying to get my head around a few loose ideas, but honestly don't have the energy to do the footwork.
 

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I did a little bit of research for a thread a little while back. Rivers and lakes average 2-3 times the CO2 concentration of normal water at equilibrium, probably due to continually decaying organic matter. So bodies of water have higher CO2 than you'd think.
 

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@kevmo911 Do you think that leaving mulm in place would produce enough additional co2 to provide some benefit a low tech tank?
 

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Rivers also have constant replacement of the water the plants are in, so rotting vegetation and other organic debris can't build up high organic breakdown products in the water where the plant is. Many rivers/creeks, where aquatic plants grow well, get a lot of their water from springs, and spring water will usually have a higher concentration of CO2 than runoff fed rivers. But, I agree that it would be a very interesting project to try a single plant with a ring of bubbles flowing through it. If you did two tanks, otherwise identical, but only one with the bubbles, you should see the effect of the bubbles.
 

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@Hoppy, What is the theory behind the higher concentrations of co2 in spring water? I'm a science geek so this stuff is fascinating to me. @Nordic thanks for posting this, it is an interesting discussion.
 

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Thanks so much for all the feedback. I might try and set up an experiment when I get a decent diffuser.
Actually thinking ring of air tube with a bunch of ordinary air stones.

I read up a bit more: I am citing an article by Karen Randal - Carbon Dioxide in Planted Freshwater Aquaria.

Plants have two different ways of finding carbon to use for growth. The first is from free carbon dioxide (CO2) captured from the water, substrate or directly from the atmosphere. In the absence of CO2, many plants have the ability to meet their carbon needs by splitting carbon directly from carbonates in the water, which is the second method.
While this second method is a useful adaptation in the wild, it is undesirable in the aquarium. When plants draw on the calcium carbonate in the water to meet their carbon needs (this process is sometimes called biogenic decalcification), the water has less and less buffering capacity, leading to serious pH fluctuations. Eventually, the plants can totally exhaust this carbon source as well.
I.e. in the presence of enough light, and absence of enough CO2 (actually Nitrogen too), we have problems.

the largest contributor to CO2 levels in the aquarium is the biofilter. In fact, a fully cycled biofilter will produce 1 gram of CO2 within 24 hours for every gram of dry food added to the tank.
Note to self: weigh amount of food given in a day and calculate CO2 ppm provided by that.


So just some random ramblings... but things to keep in mind.
 

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So if you had an automatic water change system, using an overflow and drip system, and tap water with high kh. You could utilize biogenic decalcification(BD), and not worry about using up your buffer, or ph swings.
I've read certain plants are also better at BD than other. There are some listed halfway through this article. FWHardness
 

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Discussion Starter · #9 ·
I would expect this to depend on how advanced the plant's photosynthesis process is. There are more than one mode of photosynthesis, you can look up C3 and C4 route in Google.
I have only started wading into this, and my last biology class was somewhere in 1993.
 

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One of the reasons for higher CO2 in spring water:
Water in the ground may be in contact with carbonates (Calcium carbonate, magnesium carbonate), and these dissolve, adding carbonates to the water. Some of the carbonates become CO2.
But the water is not in contact with the air, so the CO2 cannot leave the water. When this water comes to the surface it is still high in CO2. Underwater plants in such a spring can benefit from the CO2.
 

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@Diana Makes sense to me, thanks for the reply. After reading through this post I am wondering if biogenic decalcification is partially responsible for the ph drop I am seeing in my 10g shrimp tank. I had attributed the drop to the rather large piece of driftwood I have, and I am sure that is part of it. I have an Italian Val and val is one of the plants on the list in the link provided by Wilderman204. Interesting and educational thread @Nordic. Again thanks for the thread.
 

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I would expect this to depend on how advanced the plant's photosynthesis process is. There are more than one mode of photosynthesis, you can look up C3 and C4 route in Google.
I have only started wading into this, and my last biology class was somewhere in 1993.
I remember hearing Tomm Barr discuss how it is best to limit plant diversity in low tech tanks. He mentioned how some plants can photosynthesize easier than others. Those plants will outcompete the others for the limited CO2.
He also mentioned how surface agitation is important in low tech planted tanks. It helps keep CO2 constant, but at low levels. It will prevent CO2 fluctuation between the time your lights are on and off. The co2 cannot build up over night, and rapidly dissipate when the lights come back on and plants begin using it. BBA usually takes hold when CO2 levels fluctuate to much. You also need the proper balance of lighting and plant load, or gas exchange from surface agitation still won't supply enough CO2.

But I have also read others saying the CO2 buildup overnight is necessary. Some even use a mid day "siesta"(time with lights off) to allow CO2 to rise again half way through the day.
My well water has lots of trapped CO2 in it when it come out the tap. I have no high tech setups. Personally, I have found if I don't let my water gas off for a day first before my regular 50% water changes, my C02 levels fluctuate rapidly. My plants start pearling like CRAZY, but then they use up the CO2 and BBA starts to grow.
Everything seems more stable with proper surface agitation for gas exchange. I hate air stones though, the sound of air pumps and bubbles in my tank is a turn off to me. I have set my filter outputs on my Hamburg Matten Filters to create surface agitation.
 

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Discussion Starter · #13 ·
Lol, the trick with air bubbles, is to have so many going it becomes a wall of sound.
I run 7 with large air pumps.. Sacrifices are to be made if you are poor and need lots of bio filter media to keep up with stocking. :)

Just remember the question is not if you can increase CO2 with surface agitation. What I want to know is if CO2 can be targeted at a plant by having its leaves in a stream of air bubbles.
A fair range for CO2 in planted aquariums would be 15ppm (I know some run much higher), but this is only a 20th of what is in air.
 

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i have been experimenting with something like this. except i have a circulation pump that sits just under water level and pulls super tiny bits of air in and i have noticed a big difference so far. i stop running it at night though


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Lol, the trick with air bubbles, is to have so many going it becomes a wall of sound.
I run 7 with large air pumps.. Sacrifices are to be made if you are poor and need lots of bio filter media to keep up with stocking. :)

Just remember the question is not if you can increase CO2 with surface agitation. What I want to know is if CO2 can be targeted at a plant by having its leaves in a stream of air bubbles.
A fair range for CO2 in planted aquariums would be 15ppm (I know some run much higher), but this is only a 20th of what is in air.
The 400 ppm of CO2 in the atmosphere is based on volume. The 3 ppm in water is based on mass. So, the two are like apples and oranges. 400 volume ppm in air is roughly the same concentration as 3 mass ppm in water.
 

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Rain water is supposedly very high in CO2. I've used rain water in the past for replenishment for evaporation. Since our well is a surface water sourced well, I'm pretty sure the fair amount of pearling that happens when I do a 20% water change is due to the added CO2 in our well water.

I would think that a well insulated/sealed house with a few humans living in it could be creatively exploited for the increased concentration of CO2 present indoors. CO2 is heavier than air and should pool in lower areas.
 

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CO2 doesn't pool anywhere at normal temperatures. Molecular motion is very high at normal room temperatures, so air is pretty uniform from floor to ceiling, as far as the basic components of air are concerned.
 

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When I began looking for way's to get better result's with my low tech affair's, I began reading on way's carbon can be produced in the aquarium without injection of CO2 and or supplement's.
Happened upon a few articles/paper's discussing Dissolved organic/inorganic carbon in the aquarium ,and organic carbon produced in soil's.
Is largely the reason I use dirt for substrate.
Fish produce a little CO2 as well, as by product of respiration so I keep fairly good number's.
Have used fairly good ripple on surface to help with scum/protein film but have also lowered spray bar to create no rippling at all and to be honest,,I cannot say I noted any large changes either way.
 

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Discussion Starter · #19 ·
I think by the time you have fish stocking levels that will make any real difference, they will be producing other toxins at lethal levels.
 

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I think by the time you have fish stocking levels that will make any real difference, they will be producing other toxins at lethal levels.

Takes a fair number of fish maybe so ,but in NON CO2 tanks any and all CO2 that can be found is good. And If only I can see the difference then this is good also. (For me)
I run tank's for a year or more (easily), which gives one plenty of time to observe suttle changes in growth habit's which some may never observe, cause they are running everything at full tilt,rescape they're tanks monthly it seem's,or they jumped right into high energy ,high tech ifyou will, and have the ability after some tinkering to readily increase CO2 at will.
From post's I have read here and elsewhere,more folk's gas their fish than I have lost in some year's in my crude way's.
I just keep sellin/tradin plant's and fishes,shrimp.
I do have to stay on top of maint but it's what I do once a week.:wink2:
 
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