# Sooo... An air stone will increase Co2 in a low tech?!



## Diana

It could do either. 
Look at all possible sources of CO2 into the tank, and every way it can leave the tank. Balance these in favor of increasing CO2 yet still maintain good oxygen levels for the livestock. 

1) Decomposing matter such as fallen leaves. Raises CO2, but the process is slow, so you get a small amount over a long time. This is pretty good in a low tech tank. 

2) Fish respiration. Fish breath 24/7 so this is good, too. 

Combine these 2 sources in a low tech tank, and the CO2 will rise through the night, be highest in the AM right before the lights come on, then drop through the day as the plants use the CO2. This matches the cycle in nature. 

3) CO2 enters the water from the air. 
a) If the water is not moving, then very little CO2 will enter the water, because the CO2 concentration in the water at the surface is so high that no more CO2 can enter the water. 
b) If the water is slowly circulating then the CO2 rich water from the surface will be sent lower into the tank, and the water that was lower in the tank rises until it is at the surface. The CO2 that ends up near a leaf will be removed, and this CO2 depleted water is ready to get more CO2. 
So water circulation is good. 

However, if factors 1 or 2 add a LOT of CO2, then water circulation will bring this CO2 enriched water to the surface, where some CO2 can be lost to the air. 
So water circulation is bad. 

Without testing equipment it is hard to say, but a gentle ripple at the surface is usually best. 

With testing equipment (try a drop checker) you could figure out exactly how much water movement is just right for your tank to optimize the CO2 for the plants.


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## BulletToothBoris

So frustrating... But thanks


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## BulletToothBoris

I guess my question is about the video. Is he correct?


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## fishophile

Without an addition of Co2 fe it DIY, pressurized, or liquid you really aren't going to achieve any level that much higher than what is at your particular atmospheric pressure. Like stated before if anything the bubbles will just increase circulation and therefore speeding up diffusion. If you have a lot of decaying matter this may lower the CO2 levels. It's hard to say what the exact number will be and for the real world it doesn't matter. It won't really change how you'd go about keeping a low tech tank.

I personally dislike the look of large bubbles so I just use a circulation pump to ensure that nutrients are passing by the plant leaves.


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## roostertech

"liquid carbon" is not really co2 but stuff that plan can metabolize to get co2. So if that is your only source of co2 then offgassing from bubbler or surface agitation would have no effect.

If I remember correctly, the natural concentration of co2 in water less than 10ppm, often time ~2ppm. So a drop checker won't show any effect since you need at least .5ph change (~15ppm) to see visible difference in 4dKH solution. I have tried using 2dKH to get higher sensitivity in lower range w/o success.

IMO, unless you are injecting DIY,pressurized co2, bubble away.


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## AWolf

roostertech said:


> "liquid carbon" is not really co2 but stuff that plan can metabolize to get co2. So if that is your only source of co2 then offgassing from bubbler or surface agitation would have no effect.
> 
> If I remember correctly, the natural concentration of co2 in water less than 10ppm, often time ~2ppm. So a drop checker won't show any effect since you need at least .5ph change (~15ppm) to see visible difference in 4dKH solution. I have tried using 2dKH to get higher sensitivity in lower range w/o success.
> 
> IMO, unless you are injecting DIY,pressurized co2, bubble away.


I agree. I have just added the long wand LED fine bubblers to my tanks because I like the look, the fish love to play in them, and it really moves the water around. Everything in my tank is gently swaying. I found that was hard to get with a powerhead. I like that movement. On three of my tanks the bubbles only come on at night for about 5 hrs. The LED's & bubbles are beautiful at night.


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## PhilipS

Watch your pH and KH.

The CO2/PH/KH chart can help determine the CO2 dissolved in the tank.


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## 691175002

This topic is not nearly as controversial as he makes it out to be.

An airstone will push the water towards an "equilibrium" level of CO2 - basically what is naturally found in water when nothing is producing or consuming CO2.


If there are major sources of CO2 already present in the water (artificial injection, decaying matter) it is likely that the water is already above equilibrium and an airstone will gas off the extra CO2. This is likely to be the case in dirt/soil based low-tech systems, especially if you are also adding leaf litter and allowing mulm to accumulate in the tank.

If you are running a more traditional low-tech tank with mostly inert substrate it is probable that the plants are consuming more CO2 than is being produced, and an airstone will lift the CO2 levels back towards equilibrium.

An airstone does not contain any magic that makes it more effective than plain old surface agitation. The myth that finer bubbles produce more effective aeration died about 40 years ago so I was surprised to see it come up again in this video: Mis-tech | The Skeptical Aquarist


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## AWolf

691175002 said:


> An airstone does not contain any magic that makes it more effective than plain old surface agitation. The myth that finer bubbles produce more effective aeration died about 40 years ago so I was surprised to see it come up again in this video: Mis-tech | The Skeptical Aquarist


To that end, a long wand type air bubbler will roll your water nicely, and give you surface agitation. I have watched the particles in my water roll down and then back up, and around again, using a wand type bubbler. The small air stones didn't roll the water as well for me in my 10 gallons and 55g tanks. If you were to ever add CO2, just shut off the air for the daytime, while the CO2 is running. At night, when CO2 is not running, run your air.


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## BulletToothBoris

Thanks for the info all. I ordered a 800 GPH wave maker for surface agitation and circulation.


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## Mxx

Interesting question, and I was searching for an answer to this question precisely when I found this thread. 

I have a new dirted low-tech nano tank in a bedroom with a timer for the pump (and lights) so it only turns on during the day (as although quiet it still does produce some noise). As it is heavily planted I presume that CO2 levels likely get depleted during the day when the lights are on. And therefore surface agitation/circulation would initially decrease co2 levels in the morning but then increase them later in the day? 

*QUESTION* - Are C02 levels in equilibrium with the atmosphere sufficient for healthy plants and limiting algae? (Presuming other factors such as lighting and nutrient levels are appropriate). 

From what I read while trying to look it up, atmospheric CO2 is about 350ppm, and thus CO2 equilibrium in water at 23 celsius is only 0.5ppm, but ideally we'd of course want to be 20-40ppm which is quite a difference. 

Can anyone advise what sort of CO2 levels their dropcheckers indicate in their low-tech planted tanks throughout the day?

I might switch the lights & pump to morning and evening to give a siesta during the day, but I might need to dose liquid carbon as well.


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## 691175002

Mxx said:


> Are C02 levels in equilibrium with the atmosphere sufficient for healthy plants and limiting algae?


Equilibrium CO2 is sufficient to keep away algae (hence the success of low-tech tanks) but you need to limit your lighting as well, which restricts the types of plants you can keep (and the speed at which they will grow).



Mxx said:


> CO2 equilibrium in water at 23 celsius is only 0.5ppm, but ideally we'd of course want to be 20-40ppm which is quite a difference. Can anyone advise what sort of CO2 levels their dropcheckers indicate in their low-tech planted tanks throughout the day?


I aim for 10-15ppm in my tanks, I think people in general focus too hard on maximizing each individual parameter when it is sufficient to have "reasonable" amounts of light, ferts, and CO2. You have very little margin of safety when chasing extremes (and all you get is faster growth/more work trimming).

A drop checker in a low tech tank is unlikely to change color, they are pretty coarse instruments. If you made a special solution of say 1dKH you might be able to get some color.


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## AbbeysDad

The general consensus on this seems to be that breaking the surface, air bubbles cause a gas exchange that will equalize the O2/CO2 in the water with the atmosphere. Relatively speaking, any excess CO2 would be replaced by O2 and vice versa. So, in theory, CO2 could be added to the water in some tanks. However, in most tanks, CO2 would likely be replaced with O2.
Where it gets 'fuzzy' in the planted tank when CO2 is added/injected. Too much CO2 (and too little O2) can gas the fish. Since plants only use CO2 when there is light, it is often a practice to inject CO2 during periods of light and run an air pump at night. In theory, this could elevate the levels of both CO2 and O2.
(I know - the water is muddy in this area [pardon the pun])


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