CO2 after water changes and an experiment

livionakano

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Jan 24, 2005
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I had 28-52% increase for O2 for the CO2 mist method and about 40-60% for the air exposure treatment. That's a lot more growth increase than folks normally ever see.
This numbers are separated and independent variables, there are an addictive effect or there is an maximum degree of increase? (if I do both methods, should I observe 28-62 + 40-60 % increase for O2?)

The exposure treatment could be compared to hydroponic Flood and Drain System, where roots are exposed alternatedly to air and hydroponic solution ?

So, would be better to start the CO2 mist some minutes before the lights on, for an additional increase in plants health? I am using a single timer for lights and CO2 solenoid valve.

Can be the same effect observed if we put a glass with air, inverted (like a bell position) and expose for some minutes the plants that are on the botton, or close to it, like carpets or anubias, and for this reason can´t be exposed to air during WC ?

Regards,

Livio
 

Tom Barr

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I had not thought about using hydroponic root systems for the potential for storing O2 and CO2 etc.
Mainly just focusing on the shoot, as it's the part that does the O2 production.

The data just gives the ranges I measured over the same time frames on several tanks.

There is noit an additive effect.
I think exposure to pure CO2 gas ut of the water would produce the strongest O2 production afterwards.

Air would be second followed by the thick viscous medium of water with CO2 mist+ good dissolved CO2, then finally CO2 all dissolved with no non dissolved gas phase.

That's what I would predict anyway.


The goal here is not so much to have folks drain their tanks down to 95%, that's impractical with fish and other issues. It's the learn a bit more about how algae and plant production/growth rates are effected by O2 and CO2.

Few do much thinking about CO2, they would rather waste all their time on haggling over NO3 and PO4, or Ca and Mg.
Those are important as well, but CO2 is 40-50X more important in terms of dry weight biomass.

When we see dramatic increases in pearling, we should figure out a good way to measure that increase.

O2 meters are about the best measurement tool we have for that. But perhaps observations alone can help other folks.
It might not work, but we have to try:)

I think we still can see some evidence that the gas phases do increase growth and pearling with these methods not using an O2 meter.

One thing to think about is how might we be able to produce that much pearling and growth all week long and not just after the water change?
You need to see that intense pearling, health and growth first........then you have a max growth rate to compare to.

That is now your goal, the bar you set to achieve for your tank's growth.
You also should focus on CO2 if you use EI, EI rules out the nutrients leaving only the CO2 as the dependent variable.

We can deliver the CO2 a number of ways.
ADA and many other delivery in the gas and dissolved phase.
A combination of both appears to provide the best growth and what I would hypothesize.

So CO2 gas phase + dissolved would give the best results.

We are limited by practical matter with exposure to air or pure CO2 gas for brief periods, but we might observe and learn from those exposures and observations also;)

Many folks find that when they switch to CO2 mist, they have almost too much pearling, intense growth etc and algae makes a hasty retreat.
Other folks appear not to have much luck, but it might be they have not set the tank up right etc, not adding enough CO2, have other confounding issues with their independent variables etc.

Yes, it is ideal I would think to have CO2 come on about 1/2 hour before the lights come on. Then shut off about 30-60 minutes before the lights go off.

That way, as soon as the lights come on, the plants have plenty of CO2 and get going right away.


You might try the glass air bubble method to see.
I would also suggest looking at the DIY internal venturi diffuser I designed, it acts like the glass a little bit.

If you place the downward firing gas mist diffuser above a plant, it will grow very intensely compared to a similar plant on the other side of say a 4 ft long tank.

Now the pH will be the same throughout the tank mind you, but the growth will be different.

So the dissolved CO2 is fairly even, but the gas phase is the main difference in the treatments.

There are many designs you might try out here, but proving them will generally require a DO meter and relate that to growth rates.

Regards,
Tom Barr
 

cousinkenni

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May 18, 2005
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Hi Tom and others,

It is funny that I came across this thread for the first time today. Last week I was looking at my two 10g rotala tanks and I noticed a huge increase in pearling after doing my normal 90% water changes on the (left) rotala tank. Although this left tank pearls during the day, after a water change the tanks pearls like crazy. The right tank will also increase in pearling, but not as much because it already pearls like crazy. [by the way Tom, the one I was having trouble with (the left one) I ripped down, vacumed the gravel, cleaned the filter, replanted and now it is doing way better, still not up to its potential, but way better]

So to continue on.......I don't think this is actually due to CO2 in the water from the pipes because the water from the pipes is about 40ppm KH and a pH of almost 7 wich leaves the CO2 in the single digits (I will varify the CO2 content of the tap water as soon as I order some certified 4degreeKH water from Bill? for my drop checker.). I was planning on doing a negative control experiment next water change where I do the change about 3 hrs before the lights come on........If pearling occurs with the lights off then you know it is offgassing of other gasses dissolved in the water...........If I don't see the pearling within 15-30mins (about the normal time it takes to see the pearling with lights on) then I can assume that the pearling is due to one of two things: 1) exposure to CO2 from the water (unlikely see above) or the air (very likely as explained by Tom ealier in this thread).

The other interesting thing I have noticed is the left tank which actually has more CO2 dissolved in it than the right tank doesn't grow as well and doesn't pearl as much as the right tank, which has less CO2 (I determined the CO2 content by testing pH of the water in each aquarium and comparing the colors side by side; and by using the drop checkers in the aquariums with homemade 4degree KH solution). How could this be you ask? Well although the tanks are identical in every detail including the CO2 diffusor used, the left tank's CO2 diffuser doesn't work as well as the right tank's diffuser. The diffusor on the left realeases way bigger bubbles that go straight to the surface whereas the right diffusor releases tiny tiny bubbles of CO2 that go everywhere in the tank.

When I first setup both tanks I was wondering why the left tank was doing so bad........each tank had the same number of CO2 BPS. When I compared the tanks pH's side by side the left tank was always bluer. To compensate for the lower CO2 I started raising the BPS on the left tank which still didn't make the plants pearl like the right tank. Now I am at the stage where the left tank actually has more CO2 and it still isn't doing as well. This has to be due to the fine mist of CO2 that the right diffusor produces.

After I do the water change experiment this week I plan on switching the CO2 diffusors to see if this make a difference. If the left tank all of a sudden starts going crazy then it is obviously the CO2 mist not just how much dissolved CO2 is present in the water.

Anyway thats my experience thus far.

On another note I am having a problem with the drop checker returning to blue the next moring......I already read posts in other threads so I am going to buy the calibrated solution and move the drop checker in a higher flow area to see if that helps. I am using the ADA idicator solution that came with the drop checker. If the drop checker is still green the next moring I am going to raise the filter outflow to create more surface agitation. The flow rate is rediculous for this tank as it is (no glass on top, a fluval 104, 10g tank, and the outflow flows straight across the front of the tank)


Ken T.
 

Tom Barr

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The idea behind this experiment is to get folks thinking about such things.
To show that testing CO2 and O2 are important and have profound effects on growth.

Some cases will not lead the person to conclude this effect is real, but with good measurement tools, you can get a better comparison of these various tank differences and address such issues.

The goal is really to have a better understanding of CO2 and O2 production in our tanks and address many of these assumptions.
We must try these assumptions and see if they are reasonable

Without testing and thinking about it in this context, many will never see/learn more about it. Given it's critical role, that would not be wise.

I have the equipment and measurement methods available to do the work and test.

Most aquarist do not and remain, at least some, unconvinced.
I am trying to address methods that might allow them to test and rationalize it without buying DO meter and spending a lot of time measuring things.
There are trade offs with this less sophisticated method, but also some nice effects in the routine(lots of pearling).

Regards,
Tom Barr
 

cousinkenni

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May 18, 2005
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Hey All,

So I did that experiment (negative control) I was talking about in my previous post:

Water Change + No Light = no Pearling

I checked my Tap water using my Drop Checker with home made KH4 solution) and it stayed blue indicating a lack of CO2 in my tap water (I just got my KH4 reference solution from Bill right this moment so I will do another experiment tonight to double check)

This means that Light is required to induce the pearling meaning that the bubles aren't from degassing of CO2, O2, N2 or methane from the water. The bubbles are deffinately being produced by the plants in the presence of light (Photosynthesis). On top of that, since the source of CO2 isn't coming from my tap water, it must be coming from the exposure to air (in concordance with what Tom has been saying!).

Ken T.
 

Tom Barr

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I often wonder about this type of stuff when I do it and wonder and really hope others can demonstrate it also. Then I know I'm not a nut.
Well, perhaps I am, but it's nice when folks actually try such things out and see for themselves. I get awful tired of critics that never do jack:rolleyes:

They say today's mighty oak is yestderday's nut that held it's ground.
Would not be the first time.

I'd try it again though.
Think about all the other things you may have overlooked.

My question is less that there is an effect that increases O2, rather, how much and can this level of O2 production be maintained and for how long?

Could we do this daily if there's a problem with growth/algae etc?
I do not like chemical treatment of algae, I think amplification of plant growth and manual removal methods are best.

Some have disagreed, but I think this offers a new tool to help folks see what the potential is and also to help beat back algae at the same time.

Also, make sure you time the exposure to air.
How much is optimal here?

Such questions are harder to answer and you need to measure O2 levels over time to get a feel for that.

So a 10 minute exposure might yield a 10% increase for 2 hours in the O2 production rate at the peak(sort of a sharp peak with along tail after), while a 30 minute exposure (this would require misting the plants with water to prevent them from drying out) might yeild say 15% for 3 hours etc.

What is the maximum we can squeeze out of the plant for a given light level?

Those are much more interesting questions.

Regards,
Tom Barr