Mini Griggs reactor - The Planted Tank Forum
 
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post #1 of 8 (permalink) Old 12-17-2015, 07:59 PM Thread Starter
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Mini Griggs reactor

Has anyone tried to scale down the diameter on a Griggs to run it with a smaller flow rate? I have an Eheim 2213 and I hooked it up to an aqua medic reactor to see, but there is clearly not enough flow. The bubbles shoot right to the top of the reactor and co2 collects there.
I was thinking a 24inch reactor but maybe 3/4 to 1" maybe. Just wondering if anyone had tried this. Surely there is a way to scale down the diameter to match the slower flow from the filter.

Hopefully someone will do the calculations for me.


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post #2 of 8 (permalink) Old 12-18-2015, 04:55 AM
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What you look for is that the CO2 does not leave the reactor as gas bubbles. Scale down build and test - if it passes the test then its OK.

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post #3 of 8 (permalink) Old 12-18-2015, 07:12 AM
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Quote:
Originally Posted by essabee View Post
What you look for is that the CO2 does not leave the reactor as gas bubbles. Scale down build and test - if it passes the test then its OK.
That gets me thinking. Narrow at the top and wide at the bottom would probably give better agitation of the CO2 bubbles, while providing a trap at the bottom (slow water flow) to prevent them from shooting into the return tube. I'm think the reactor should be a cone.

Ok, so finding the materials to make a cone would be a challenge, but you could use a few different diameter sections of pvc. Maybe 1", 1.5", and 2". Each section would be about 8" long. That would be for a lower flow setup. For most setups, I'm guessing few to no bubbles would remain in the 1" section. Too much flow, so maybe start with 1.25". IDK, just thinking out loud here.
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post #4 of 8 (permalink) Old 12-18-2015, 07:24 AM
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There is another way too - if the exit pipe is narrow and the pressure inside the reactor increases - then the rate of diffusion of CO2 should increase.

Theoretical - but a lot of parameters to play with - that's what makes DIY so interesting especially when treading untraveled paths.

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Last edited by essabee; 12-18-2015 at 07:25 AM. Reason: grammar
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post #5 of 8 (permalink) Old 12-18-2015, 07:45 AM
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Before you scrap the Aqua Medic, give it some time. If the gas starts building up at the top of the reactor, then there will be more turbulence as the vertical section of gas increases. Give it until the end of the lighting period and then decide.

Bump: ...But yes, the higher the flow value, the larger the diameter of the reactor that is ideal. So it should, theoretically, work the same in reverse. Just trying to save you some work and cash.
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post #6 of 8 (permalink) Old 12-18-2015, 08:25 AM Thread Starter
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I won't scrap it, I'll use it somewhere else. It just got me thinking about a mini reactor. And it's expensive to do trial and error with clear pvc. Without clear pvc it's also hard to know exactly what's going on inside. It could all be collecting in the top of the reactor and you wouldn't know other than maybe with noise. I have my Cerges tuned really well. I barely see any bubbles in the chamber, if I do they are super small. A lot of the Cerges videos I see have bubbles dancing in the reactor. Mine has barely any.
It also makes me think that maybe we should be injecting CO2 right at the output of the canister, not at the Cerges. To increase the contact time prior to getting to the reactor.

Last edited by The Big Buddha; 12-18-2015 at 08:29 AM. Reason: Fix
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post #7 of 8 (permalink) Old 12-23-2015, 03:32 PM
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I think scaling down can work but the design may need to be modified.
There are commercial co2 reactors that are quite small, they resemble a cerges reactor more, though i think their main benefit is that their intake comes in from the side of the cylinder rather than the top, i assume this creates a vortex effect in the reactor which increases dwell time.
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post #8 of 8 (permalink) Old 12-23-2015, 04:32 PM
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This little bugger is still sitting on the workbench....will get to it someday!

https://www.plantedtank.net/forums/20...s-reactor.html

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