Griggs Reactor question - The Planted Tank Forum
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post #1 of 10 (permalink) Old 05-09-2018, 02:18 AM Thread Starter
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Griggs Reactor question

Building a Rex Griggs Reactor and I'm not sure where to place the CO2. The reactor will be 4" diameter and 20" in length. Barb fitting, tee fitting, then reducing coupler. The plan is to use a sprinkler riser to act as a compression fitting to allow the Co2 line to be pulled to the center of the reactor placed in the input water flows direct path. But I'm not sure how far down into the reactor the end of the co2 should be.

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I have searched many Griggs reactor threads and there doesn't seem to be a definitive placement. Some say as close to the top of the reactor possible and others say closer towards the bottom but not so close to getting pushed out the output. So the CO2 bubbles have to float up to the top and be pushed back from the flow. Would anyone want to share what they chose for their reactor and how effective your choice is working? Or if you were to build this reactor where would you cut the Co2 tubing?


Also one other question. Is there a direct relation to the more co2 injected the higher flow is needed to reduce a co2 bubble from forming?


Thank you,

David
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post #2 of 10 (permalink) Old 05-09-2018, 02:39 AM
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Can only offer you what I did with my setup. CO2 input is not exactly at the actual input to the reactor - pretty sure it would not matter.





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post #3 of 10 (permalink) Old 05-09-2018, 03:22 AM Thread Starter
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That's a cerges reactor. I tried a cerges reactor already, however, it couldn't meet the CO2 injection demand on my setup without forming a gas buildup on the top of the reactor. That being said, are you saying that your vote is make the Co2 close to the top or even before the reactor?
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post #4 of 10 (permalink) Old 05-09-2018, 04:16 AM
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You should put the CO2 entry near the top. As the water flow enters the reactor, it pushes the bubbles down. The closer to the exit the CO2 input is, the more likely the bubbles will be pushed through before they can circulate in the reactor. You can see this in a clear reactor.

I assume that the "bubble from forming" you mention is the CO2 gap that forms at the top. The water does not have instant potential to absorb CO2 in the small space of the reactor (pressure helps). Some of the bubbles will float along the sides, after being pushed down by the flow, and merge at the top into what will become a growing gap. Higher flow, beyond whatever is optimal for your reactor, will simply push more bubbles out of the reactor and into the tank. The CO2 gap that does form will be absorbed when the CO2 is off at night ...assuming you aren't running it 24/7.
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post #5 of 10 (permalink) Old 05-09-2018, 05:00 AM Thread Starter
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How far down? Would you say right where the tee fitting connects to the reducing coupler? Or would having it extend further to where the coupler begins to expand?

Yes, the bubble forming was a Co2 gap. This was when I was using a cerges reactor. I am hoping switching to a rex griggs reactor would prevent this from occurring. I even had valves pre and post cerges reactor and no matter how I adjusted them I just couldn't seem to find the balance of CO2 absorption to achieve a 1 degree PH drop without getting a huge CO2 gap. It was like 3/4 of the reactor.

What do you mean pressure helps? Backpressure post reactor with a valve?

Was I wrong in my assumption that the more CO2 injected means a higher flow needed for fresh water to absorb the C02?

My plan to dial in the rex griggs reactor is to first purge air after initial setup. After the air has been evacuated start injecting CO2. Set input flow to where the CO2 is getting pummeled. Once I begin to see micro bubbles flowing down towards the bottom add backpressure using a valve I will install on the reactor's output. Or at least this is my plan, however, one thing I've learned is nothing ever goes according to plan.

I don't plan to run 24/7. I have a neptune apex and the plan is to inject CO2 at a high rate and have the apex control the Regulator via PH to my target PH range. I will initially set the CO2 to turn on 2 hours prior to lights and monitor how long the reactor takes for CO2 to make the 1 degree PH drop and adjust accordingly. Then start turning bps down until I get the exact amount needed to maintain the PH. So I'm not just dumping CO2 and needing the regulator constantly cycle on and off. This should help prolong the life of the regulator. I'm guessing around 10 bps initially and hopefully, with this reactors efficiency will dial down to 8 bps or maybe even less. I have no doubt that I need a higher bubble count on this size of an aquarium (180g).

I have never had this much trouble setting up a tank before. I have set up many planted tanks but until this one, the largest was a 75g. They were all so easy. I did my research on tanks with sumps and had a really solid plan prior to even getting this aquarium setup. However, like I stated before nothing has gone according to plan with this setup, lol. Not necessarily all bad but has definitely been a learning experience.
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post #6 of 10 (permalink) Old 05-09-2018, 04:13 PM
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With 4” diameter and 20” length, you should be able to have pretty good flow, without pushing bubbles through, and enough to give you at least a 1-point pH drop.

In a standard Griggs design, I place the CO2 line about 3” below the point of water entry into the reactor.

Quote:
Backpressure post reactor with a valve?
Exactly. It doesn’t create much pressure, but does help dissolve the bubbles. You have to balance it against the amount of gph you want moving into your tank. I think that your plan should work.

In my case, my reactor is before the filter, which creates a larger gap than when it is placed after the filter. So I have devised a ‘silencer’ (gurgling too loud) that works to minimize the CO2 gap by converting the gap into more bubbles. This would probably work on an after-filter design as well, but it’s still being tested.
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post #7 of 10 (permalink) Old 05-09-2018, 05:17 PM
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Here's mine. Also a 20" filter, 120G tank, heavy CO2 injection, never a hint of a bubble.

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post #8 of 10 (permalink) Old 05-09-2018, 05:57 PM Thread Starter
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Quote:
Originally Posted by Deanna View Post
With 4” diameter and 20” length, you should be able to have pretty good flow, without pushing bubbles through, and enough to give you at least a 1-point pH drop.

In a standard Griggs design, I place the CO2 line about 3” below the point of water entry into the reactor.

Exactly. It doesn’t create much pressure, but does help dissolve the bubbles. You have to balance it against the amount of gph you want moving into your tank. I think that your plan should work.

In my case, my reactor is before the filter, which creates a larger gap than when it is placed after the filter. So I have devised a ‘silencer’ (gurgling too loud) that works to minimize the CO2 gap by converting the gap into more bubbles. This would probably work on an after-filter design as well, but it’s still being tested.

3" down sounds good. I think I've read one other thread searching through all the griggs reactor threads where someone recommended 2". Seems like the best placement is in that range for the CO2 injection point.

I'm also thinking that I may drill a hole and add a tube to purge the reactor. This will be sitting in the return chamber of my sump and there will not be space for me to invert the reactor to purge the air.

I'd be interested in the silencer once you have tested, just in case I do get gas buildup.
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post #9 of 10 (permalink) Old 05-09-2018, 06:07 PM
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Quote:
Originally Posted by dj2606 View Post
I'd be interested in the silencer once you have tested, just in case I do get gas buildup.
I'll be posting here: https://www.plantedtank.net/forums/9-...-filter-4.html

Probably by the end of May. Just fine-tuning it over the next few weeks.

There is also other interesting info, on that thread, regarding some of your questions.
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post #10 of 10 (permalink) Old 05-13-2018, 12:14 AM
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When faced with design questions, I like to avoid reinventing the wheel if at all possible and there is a good working model to be found. So the Grigg's design is super enough to almost be a "standard" in reactors. That leaves me asking if I am really wizard enough to improve what the old boy did? I'm not that bold so I look for the closest thing to the original and totally resist the urge to "improve" it by adding or changing things.
This is my "bible" and it has always worked so I'm not changing!!!
How To Build A CO2 Reactor | Build a Regulator | Test Kit
I have used them on tanks from 20 long to 120 and they just simply work. Or is it work simply? No bells, no whistles needed, just simple.
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