# Rex Grigg Reactor



## sfshrimp (May 24, 2016)

Could you make one out of a reactor like this? Or would you need another pump to get water up into the tank?

https://www.youtube.com/watch?v=0qI2Y-DHzQs


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## user12345pk (Sep 7, 2016)

like this

How To Build A CO2 Reactor | Build a Regulator | Test Kit


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## sfshrimp (May 24, 2016)

user12345pk said:


> like this
> 
> How To Build A CO2 Reactor | Build a Regulator | Test Kit


Perfect - thanks for this info. My only worry is if there would be enough pressure from the canister's out (eheim 2213) to supply sufficient flow. It's a pretty low output filter < 75-100GPH I'd guess.


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## user12345pk (Sep 7, 2016)

this shouldn't be a problem. i have the eheim 250 (2213) and i have both the reactor and uv light hooked up and the flow seems ok to me.
check out this video

video link


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## PlantedRich (Jul 21, 2010)

Definitely recommend doing it exactly as shown. I find simple is really the best way to go on this reactor. 
But then I do have one small thing that you may consider or not. Rex had worked out 99.9 % of the bugs but I like to use a straight fitting at the top rather than a 90 elbow. Corners make water flow slow just a bit so if we use have the space and can make a large sweeping turn in the tubing going into the reactor, it may help to avoid slowing the flow. Not a big thing if all is okay but when we worry about the flow, I like to remove as many questions as possible. 
I'm kind of hyper about the flow on my filters as I never seem to have too much.


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## sdwindansea (Oct 28, 2016)

@PlantedRich, how do you secure the CO2 line to the reactor? Do you just drill the hole and use a bit of silicon? Or is there a better way that would make maintenance easier as well?


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## PlantedRich (Jul 21, 2010)

That part is one of the most frequently changed things on the Grigg's. The original design uses a small hole with the tubing drawn through so that it expands and seals itself. This works and is what I have used on all my reactors except one built using 3/4 " pipe. The advantages and disadvantages are often debated. 
Many, like yourself, are really concerned about how it is fastened and holds without leaking. Real concern and fully understood!!! No argument from me on the concern. 
But then there are times when I think I see a downside. No proof but just what I "feel" might be a problem. 
Folks often use a fitting to attach the tubing. something like a barb fitting that screws into the PVC. The downside may be "I feel" that the fitting does let the CO2 come out in the center of the water flow but at the side wall of the PVC. Playing around creeks, rivers, etc. you may have noticed that the edges of water tend to flow slower than the center of a channel. I see this in pipes as well. So I feel what may happen is the CO2 is released in an area where there is little resistance to the bubble going up to the top and forming a large bubbles gap. This gap can make noise from splashing. 
I still use the undersized hole and pull the tubing through enough so that it lets the CO2 bubble out in mid-stream. Never leaks and the cheap airline tubing I use has not needed to be replaced after several years use so I still go with the original plan. 
Trying not to shoot myself in the foot due to thinking harder than needed!!


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## sdwindansea (Oct 28, 2016)

Thanks as always @PlantedRich and great to hear. I have a feeling I will be building one sooner than later for my 60 gallon. Just getting started with CO2 so taking it slowly. Once I get to that point I'm sure I'll have some specific questions related to my setup (diameter of pipe, length of pipe, etc.).


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## PlantedRich (Jul 21, 2010)

There are always things that we need to adjust as we go but the reactor seems to be one that has more faults if we go small. Large gets into our way and costs more as much as anything else. Part of the sizing is how fast the water is flowing through as that is what blows the bubbles out into the tank, how much CO2 as that determines how long it needs to stay in the reactor. 
So I find this reactor is good using about 15-18 inches of 1 1/2 inch PVC. It gets about 20-21 inches when the fittings are added. Notice the extra coupling? I moved it from using it on an Eheim 2217 on a 75 gallon to use the same filter on a 125 gallon where I'm pumping lots more CO2. It worked well on both tanks but when moving, I wanted to change out the airline so cut the pipe open to let me pull the new tubing in with pliers. 
Next time I need to change the tubing, I won't have enough PVC left to do the same again but then if it lasts five years, I can go for cutting the top fittings off and using new, about $5-6 is okay if no more often than that.


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## sfshrimp (May 24, 2016)

PlantedRich said:


> There are always things that we need to adjust as we go but the reactor seems to be one that has more faults if we go small. Large gets into our way and costs more as much as anything else. Part of the sizing is how fast the water is flowing through as that is what blows the bubbles out into the tank, how much CO2 as that determines how long it needs to stay in the reactor.
> So I find this reactor is good using about 15-18 inches of 1 1/2 inch PVC. It gets about 20-21 inches when the fittings are added. Notice the extra coupling? I moved it from using it on an Eheim 2217 on a 75 gallon to use the same filter on a 125 gallon where I'm pumping lots more CO2. It worked well on both tanks but when moving, I wanted to change out the airline so cut the pipe open to let me pull the new tubing in with pliers.
> Next time I need to change the tubing, I won't have enough PVC left to do the same again but then if it lasts five years, I can go for cutting the top fittings off and using new, about $5-6 is okay if no more often than that.


Why couldn't you inject the c02 directly into the cannister? It seems like a waste of space to have another pipe just for the outflow?


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## natemcnutty (May 26, 2016)

sfshrimp said:


> Why couldn't you inject the c02 directly into the cannister? It seems like a waste of space to have another pipe just for the outflow?


Risk of damaging your canister. Even when using the impeller to chop up the bubbles, those bubbles can get trapped in the canister over time and eventually pool up and cause the pump itself to run dry. It can also be a bit noisy which may matter of you have a tank in your bedroom as I do


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## PlantedRich (Jul 21, 2010)

I have not tried it on a larger canister but I see potential for problems. I Did try it on a small Zoomed 501 canister and it seemed to work for a time as I was first starting and running very low level CO2 to see how much I needed before getting too far and gassing any fish. What I found was that it was okay for a time but as I turned more CO2 in on the intake side, I began to get more and more collecting in the top of the canister. finally as I increased the flow, I went in to check and found the bubble of CO2 in the top of the canister was large enough to keep the impeller from getting water. In my case, it did not harm the impeller but then I did not let it run more than 30-40 minutes before I caught it. Had it been a time when I was gone, etc. running it dry would have almost certainly scored the impeller.


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## sfshrimp (May 24, 2016)

PlantedRich said:


> I have not tried it on a larger canister but I see potential for problems. I Did try it on a small Zoomed 501 canister and it seemed to work for a time as I was first starting and running very low level CO2 to see how much I needed before getting too far and gassing any fish. What I found was that it was okay for a time but as I turned more CO2 in on the intake side, I began to get more and more collecting in the top of the canister. finally as I increased the flow, I went in to check and found the bubble of CO2 in the top of the canister was large enough to keep the impeller from getting water. In my case, it did not harm the impeller but then I did not let it run more than 30-40 minutes before I caught it. Had it been a time when I was gone, etc. running it dry would have almost certainly scored the impeller.


Nm, this makes a lot of sense. Putting air in the canister probably doesn't make sense. It would be funny to blow the top of the can.:surprise:


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## Botia dude (Feb 6, 2005)

I just built one of these Rex style diffusers over the weekend. Total length is maybe 16-18", I haven't measured. I let it cure for about 6-8 hrs before I touched it. 2 hrs was what the cement bottle said but even after rinsing and soaking it I'm still getting a chemical odor from the glue inside. Safe to hook up and run or should I just let it sit dry for a few more days? Currently have it soaking in a bucket of tap water.


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## sdwindansea (Oct 28, 2016)

Botia dude said:


> I just built one of these Rex style diffusers over the weekend. Total length is maybe 16-18", I haven't measured. I let it cure for about 6-8 hrs before I touched it. 2 hrs was what the cement bottle said but even after rinsing and soaking it I'm still getting a chemical odor from the glue inside. Safe to hook up and run or should I just let it sit dry for a few more days? Currently have it soaking in a bucket of tap water.


Did you use PVC with PVC primer and cement? I do not believe the cure time is more than a couple of minutes. Or did you use ABS? Something different?


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## Botia dude (Feb 6, 2005)

Standard schedule 40 pvc with pvc primer and cement. It's been soaking overnight I'll let it dry and check again for odor.


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## sdwindansea (Oct 28, 2016)

You should be fine then. I've done a lot of work with PVC and it typically is fine under pressure if you use primer/cement after a couple of minutes.


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## user12345pk (Sep 7, 2016)

i used mine about 30 min in , no shrimp death.


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## Botia dude (Feb 6, 2005)

sdwindansea said:


> You should be fine then. I've done a lot of work with PVC and it typically is fine under pressure if you use primer/cement after a couple of minutes.





user12345pk said:


> i used mine about 30 min in , no shrimp death.


Thanks. The smell has been much reduced after an overnight soak. I was just concerned about potential residues absorbing into the Substrate or wood. If i'd left one screw in pc off it probably would have dissipated much sooner.


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## PlantedRich (Jul 21, 2010)

On this point, I feel it is not a big question of the weld holding as I often do PVC and put tap pressure back within minutes. However, I do not use it for tanks until I wait much longer. I judge when it may be getting safe differently. I wait 12-24 hours and then test by smelling and before use on reactors, which tend to have very low air flow when setting, I do a further test. If the smell is not strong, I take a small gradual pull of air through the reactor and into my lungs. CAUtion----Do this with care as the fumes are BAD when too soon. But my thinking is that any fumes that choke me, should not be going into my tanks!!! I wait.


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