CO2 Reactor: How do you control CO2 dosing rates - The Planted Tank Forum
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post #1 of 18 (permalink) Old 12-14-2016, 01:43 AM Thread Starter
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CO2 Reactor: How do you control CO2 dosing rates

Hi,

This is just general discussion to share some ideas on controlling Co2 injection rates in a Cerges or Grirggs reactor, or any other CO2 reactor design. How much CO2 are you injecting? How do you regulate it? And have you seen any effects from over dosing or is it hard to overdose with your reactor design.
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post #2 of 18 (permalink) Old 12-14-2016, 03:12 AM
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A typical application includes a needle valve feeding a bubble counter then to a reactor.
The more precision the needle valve has the finer you may adjust.

All bubbles are not equal either.
The orifice size in the bubble counter can be the difference.

With an efficient reactor design you could gas all your livestock if not careful.

Adding CO2 to one's tank does not remove oxygen, it just adds CO2.


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post #3 of 18 (permalink) Old 12-14-2016, 05:50 PM
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It is extremely easy to overdose with my Rex Grigg design. It is hard to standardize co2 input because bubble counts aren't accurate as the above user stated. I have overdosed and killed a couple guppies and a few fish died later on as a result of gill damage. Injecting co2 doesn't remove oxygen as many think, but it does cause issues with fish. Imagine trying to breath air with 20% oxygen (Normal atmosphere) but instead of 78% nitrogen, it was 78% carbon dioxide. Your body would not accept that air because co2 concentration causes the urge to breath, not lack of o2. Imagine a fish trying to live in an environment where their body thinks that they are suffocating constantly, but they really are not. It is extremely stressful and that is what I think kills the fish.
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post #4 of 18 (permalink) Old 12-14-2016, 06:47 PM
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Quote:
Originally Posted by sohankpatel View Post
It is extremely easy to overdose with my Rex Grigg design. It is hard to standardize co2 input because bubble counts aren't accurate as the above user stated. I have overdosed and killed a couple guppies and a few fish died later on as a result of gill damage. Injecting co2 doesn't remove oxygen as many think, but it does cause issues with fish. Imagine trying to breath air with 20% oxygen (Normal atmosphere) but instead of 78% nitrogen, it was 78% carbon dioxide. Your body would not accept that air because co2 concentration causes the urge to breath, not lack of o2. Imagine a fish trying to live in an environment where their body thinks that they are suffocating constantly, but they really are not. It is extremely stressful and that is what I think kills the fish.
When you overdose co2 your fish do not die from stress they are suffocating. Gasses in the blood diffuse from areas of high concentration to low through the lungs in humans, and the gills in fish. When CO2 levels get too high there is no mechanism for the fish to remove CO2 from their blood, instead it continues to build up. While CO2 does not bind to the same receptors on hemoglobin as oxygen does, large concentrations do greatly reduce the capacity for it to carry oxygen.

CO2 does kill you. Not stress. Whether it be from a lack of oxygen getting to the brain resulting in brain death or the acidification of the blood through the formation of carbonic acid, you will die a very uncomfortable death. CO2 can be extremely dangerous in high levels, and in industrial settings has specific guidelines to prevent things like this from happening.
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post #5 of 18 (permalink) Old 12-14-2016, 08:05 PM
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Originally Posted by pmcarbrey View Post
When you overdose co2 your fish do not die from stress they are suffocating. Gasses in the blood diffuse from areas of high concentration to low through the lungs in humans, and the gills in fish. When CO2 levels get too high there is no mechanism for the fish to remove CO2 from their blood, instead it continues to build up. While CO2 does not bind to the same receptors on hemoglobin as oxygen does, large concentrations do greatly reduce the capacity for it to carry oxygen.

CO2 does kill you. Not stress. Whether it be from a lack of oxygen getting to the brain resulting in brain death or the acidification of the blood through the formation of carbonic acid, you will die a very uncomfortable death. CO2 can be extremely dangerous in high levels, and in industrial settings has specific guidelines to prevent things like this from happening.
Ah, thank you for correcting me. In a fish tank, I believe that stress may play a part, but in large quantities you are correct. I didn't know that it could reduce the ability of blood to carry oxygen.

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post #6 of 18 (permalink) Old 12-14-2016, 08:24 PM
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I try to provide enough surface agitation (or sump filtration) to make an overdose unlikely.

I've always found CO2 very easy to manage since the acceptable range is so wide. Really anything from 5-30ppm is fine unless you are running extremely high light.


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post #7 of 18 (permalink) Old 12-14-2016, 08:27 PM
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Originally Posted by sohankpatel View Post
Ah, thank you for correcting me. In a fish tank, I believe that stress may play a part, but in large quantities you are correct. I didn't know that it could reduce the ability of blood to carry oxygen.
Yes, got a buddy from High-school who nearly killed himself welding, tank burst valve went and he thought he could just quickly swap tanks and finish up what he was working on. He passed out right as someone was coming to check on him because of the noise, very lucky.
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post #8 of 18 (permalink) Old 12-14-2016, 08:34 PM
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Cheap or expensive is a matter of err choices.. I'm sure I could build a reactor system for more than a 2 stage atomizer system.. if I tried..

Contemplated reactors but all the "little bits" and "hosey things" made a atomizer system much more appealing..
as it is it has one "control" system opposed to 2 in your case.. and a lot of extra plumbing..
not a bad or good thing.. just a thing..

either way a regulator is needed... and brand spanking new (or used lightly) 2 stage can be had for almost free (eekbay) to $200 w/ a CGA swap..
https://weldingsupply.com/cgi-bin/ei...EF:X:35-50-580

It may not be "necessary" but even w/ a reactor "I" would probably choose a 2 stage for 1)my own want and 2)higher resale value 3)known advantages at EOT, though not particularly needed w/ a reactor..

As to needle valves SMC-As1000's work fine at under $15...

One question is what prevents an atomizer from "outgassing" in the case of excessive CO2 anyways? Should behave similar to a reactor in this sense, though smaller bubbles..hmm.
I will state that the larger the tank the more the reactor gets favored, but for under 100gal..????

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Last edited by jeffkrol; 12-14-2016 at 08:44 PM. Reason: edit
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post #9 of 18 (permalink) Old 12-14-2016, 08:35 PM
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I run 60+ppm in my tanks with rex griggs reactors(= The whole trick is gradually increasing it over a long period of time (weeks to months) Even though my rex griggs reactors diffuse 100% of the co2 I run my bubble counters at a rate so fast that it looks like a steady line of bubbles without space between. My fish and shrimp are happy and healthy. I would suggest starting at 2bps and watch a drop checker to see how much co2 you are getting (estimate).
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post #10 of 18 (permalink) Old 12-14-2016, 09:46 PM
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Personally I use a Ph controller. It monitors your Ph, and turns on your c02 until you hit a specific Ph set point, which is going to correlate to a relative co2 ppm.

I keep the co2 flow rate higher than I need to, so I get a pretty quick Ph drop. Once it hits my set point, it turns off the co2 until the Ph starts drifting up. It also allows me to more easily adjust my relative co2 ppm while observing things. Right now I am driving down my Ph from 7.6 to 6.5 and it seems to be working well. I could adjust it easily if I wanted to.

Now there's always an argument whether it's something you really need or not. My feeling is it's not something you need, but it's awfully nice to have. Same goes for drop checker. Do you really need one? No. But it's awfully nice to have.

I am using both, which really, really isn't needed. But it makes me feel better, so it's worth it to me.


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post #11 of 18 (permalink) Old 12-16-2016, 03:21 AM
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My reactor is a bit inefficient. It works out perfect in my tank in that I can get enough CO2 in for the plants, but not enough to gas the fish. I just end up burbling a big bubble of undissolved gas in the top of the reactor if I crank my bubble rate too high. My Ottos come out and hang on the front glass (sometimes don't see them for months until this happens!) Nothing else in the tank seems affected. Just dumb luck that it worked out that way.
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post #12 of 18 (permalink) Old 12-16-2016, 03:26 AM
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@rezco I would like to know more about your reactor that everyone was bashing on the other thread.
I find it interesting myself, others object when stepping out of the norm.
Some details please?


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post #13 of 18 (permalink) Old 12-16-2016, 03:36 AM
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Not sure about the bashing..Not going to bother w/ the other thread..
Sticky point seems to be the statement that one can't "overdose" fish w/ a reactor so good needle valves or regulators are really not needed.

Some have stated they have killed fish using a reactor..

Is it "A" reactor per se, or a system???

There seems to be a discrepancy somewhere that probably is muddied by using 2 threads..

Quote:
While I agree you need precise control if you are using a bubbler or diffuser - it is not necessary for a CO2 reactor and there is no value added from a expensive dual stage reg.
Implication being you can dump as much CO2 as you want and it will just burp out somewhere..
May or may not be 100% true... and fish deaths lead some credence to not 100% true..

Quote:
Carbon Dioxide solubility: 1.45g/L @ 25C.
So this means that if we could pump CO2 fast enough into our aquariums, it could reach a theoretical maximum concentration of 1450mg/L (1450ppm)?
We only want about 30ppm though, so it seems this should be 'easy' given the typical temperature for our setups is also around 25C.
So why isn't it?
Quote:
I have measured inside reactors and generally the internal pressure of the reactor relates to the amount of CO2(aq), in my do-it-yourself reactors the dissolved CO2 runs from 140-180-ppm, measured pressure is 0.124-0.0199-bar.
I also measure reactor out flow around 100-ppm, though this varies quite a bit and may relate to my measurement or sampling technique.
I find it interesting that I find a consistent 65-ppm CO2 in the downstream corner nearest the reactor. In each case the reactor output is 2⁄3 deep about 15 centimeters from the corner, the flow is from that end to the other with a slight gyre.


Biollante
http://www.barrreport.com/forum/barr...co2-solubility

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Last edited by jeffkrol; 12-16-2016 at 03:56 AM. Reason: edit
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post #14 of 18 (permalink) Old 12-16-2016, 04:13 AM
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It is a different type of reactor I believe.
I have seen such before but not on this site, nor can I find where I have seen it.
Has an extra pump too, only to saturate the water in the reactor with CO2.
Tank filter is connected through lower portion of reactor and back to tank.
It can only carry with it some water from reactor that is saturated in CO2.
Time it right and fill it up with CO2 again. Continuous CO2 flow is not needed.
Just enough equipment is needed to fill reactor to acceptable level.

We all waste CO2 I mean lets be real.
Is it worth running an extra pump in terms of electric vs. CO2 refill?
Not sure nor do I want to do the math.

Just something out of the norm like full spectrum LED's.


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post #15 of 18 (permalink) Old 12-16-2016, 04:44 AM Thread Starter
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Originally Posted by Maryland Guppy View Post
@rezco I would like to know more about your reactor that everyone was bashing on the other thread.
I find it interesting myself, others object when stepping out of the norm.
Some details please?
I described the build a few years ago here: https://www.plantedtank.net/forums/20...2-reactor.html. This design as shown is oversized (I wanted to err on the side of having too much capacity initially) and will kill your fish if you do not limit the dosing of CO2 into the reactor.

In this design the output CO2 levels are related to the size of the reactor. In my case I was able to hit 100-150ppm CO2 on discharge. By limiting the depth of the air-water interface to 4" the CO2 comes down to 40-50.

I have a arduino controller that injects a alrge amount of CO2 in the morning to bring the levels up quickly and then injects for a few minutes every hour to maintain the levels. A drop checker is used as a visual backup.

I find it easier to fine tune the dosing levels by adding/subtracting a few minutes from the dosing schedule. Much easier than measuring flow with a bubble counter.

If the same design is implemented on a smaller scale say a 2" x 12" then it could have an intrinsic safety feature because of its size that would allow excess CO2 to simply bubble out the bottom. This way it could be designed to never exceed 30ppm of CO2 while still providing fast CO2 transfer rates. I will try to draw up a diagram and post it here.
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