# I Need an Explaination of Rex Griggs Reactors Please



## Hannothan (Dec 26, 2010)

The size of the pipe lets you have more flow/gas. As you pump in CO2, your flow rate matters. If it's too much, say for a bigger aquarium, it will force the bubbles out the bottom. As I understand it, having a longer tube helps off set this.

The idea is to keep the CO2 suspended in the tube. Water will move slower through the larger diameter tube than it will through the narrower tubing. If you just injected the CO2 into your tubing from your filter, it will get blown out. There may be ways of doing it so it doesn't... worth looking into.

I thought about putting my inline diffuser before the reactor, but I decided it would be a waste. The bubbles coming out of that thing are tiny. Because of this, they will get blown out much easier and you'd likely still end up with a mist in your tank. It may help some of them dissolve faster, but they won't stay suspended in the reactor, and that would defeat it's purpose.


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## Loop (Jan 8, 2011)

OK, having lower flow from the larger diameter tube definately makes sense. I can see the bubbles just being carried through the system with too high of flow. I can't believe I didn't figure that out on my own now.

As for using the inline diffusor with it, I'm still a little confused about that. Your saying that the smaller bubbles will get blown out easier. Do the larger ones just rise to the top of the reactor and collect in a large bubble that is slowly worn down/dissolved by the water flowing by? This is the only thing I could think of based on your statement, otherwise it seemed like the large bubbles would just eventually shrink to small bubbles and be blown out just the same.

Although as I was typing that I had a different idea. When the small bubbles come out of the diffusor like a mist, they would enter the diffusor by the thousands and be blown out. On the other hand if you just let the large bubbles from a co2 bottle enter the reactor, it would only be a couple boubles per second, that would slowly be worn down individually until they were small enough to be blown out. Therefor you would only get a couple very small bubbles entering the tank per second, at approximately the same rate that they left your co2 bottle. I hope that makes sense:icon_conf Is this what you mean?


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## kevmo911 (Sep 24, 2010)

I can't help you with the chem/physics involved. I will say that I built a grigg reactor (well, a variant of it, after a couple attempts), and run about 3 bps through it, following a SunSun 264gph canister, and get zero bubbles in my tank.

I would guess (really, just a guess) that the violence of the change from tubing to a 2" opening has something to do with the mixing of CO2 gas into the liquid. I picture something along the lines of pouring Kool-Aid powder into a thermos filled with water and shaking violently, rather than pouring and then dumping it out. I doubt this helps. For the science involved, try somebody else. All I can offer is anecdotal.


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## djscotty (Sep 14, 2010)

subscribed. I am in the process of building one this weekend. I also wondered how the diameter to the length of pipe makes a difference and is there a way to know how to fine tune it?


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## Loop (Jan 8, 2011)

kevmo911 said:


> I can't help you with the chem/physics involved. I will say that I built a grigg reactor (well, a variant of it, after a couple attempts), and run about 3 bps through it, following a SunSun 264gph canister, and get zero bubbles in my tank.


With or without science, that's still good to know. 

So far I've tried a regular glass diffusor but I got some bubbles, it didn't seem like I was getting good use of the CO2 at all, and it would annoy me with the sound it made. Now I'm trying the inline, which seems to make better use of the CO2, and doesn't make any weird noises, but the crazy amount of misty bubbles make the tank look like the water is cloudy. Now I'm looking for something better. I was hoping the diffusor could still be used to get it 100% diffused, but it's not looking like a good option and doesn't seem necessary from what your saying you get. I'm using a SunSun also, so I would expect similar results. Got any info or pics on how yours is set up?


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## kevmo911 (Sep 24, 2010)

It's about 20" tall, I think. The brass barb is a 1/8" MPT thread, which fits perfectly inside a 3/8" drillbit hole, with teflon. Intake through the top (after the canister), outflow through the bottom. Tubing goes directly through a spraybar, no diffuser. Bushings are the size that Grigg recommends (3/4") with special-ordered 5/8" barbs (I got frustrated and ordered a bunch from Grainger - none available at HD/Lowe's, though 3/4" barbs will work with hot water and elbow grease). The whole setup, without specialty barbs, should cost around $25.


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## Hannothan (Dec 26, 2010)

I found 3/4 to 5/8 barbed elbow at Menards. Lowes and Home Depot had nothing.

As to the smaller bubbles being blown out easier, I'll try to explain. If you notice the small bubbles in your aquarium from your inline diffuser, they seem to linger in the water for a while. Now, hook up a regular bubbles stone to your CO2 and you'll notice the large bubbles float to the surface quickly.

The larger bubbles displace more water and have greater buoyancy. When met with downward force, like the water flowing through a reactor, it will take more force to force those bubbles down.

The smaller bubbles, that take a while to float to the surface, when met with the same water flow, will be swept away by it.

If your BPS is too high, then yes, a pocket of CO2 can collect in the top of the reactor. You may hear a splash sound coming from it. Which can cause problems after the CO2 shuts off because you'll still be dissolving CO2 in the water.

You could design a completely new reactor designed to dissolve the tiny bubbles better and reduce the mist in your aquarium. Ever seen a Seaclone protein skimmer? It creates a vortex of tiny bubbles while the water flowing back into the tanks has very little to no bubbles. I bet that design could be adapted for CO2.


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## Hannothan (Dec 26, 2010)

djscotty said:


> subscribed. I am in the process of building one this weekend. I also wondered how the diameter to the length of pipe makes a difference and is there a way to know how to fine tune it?


I'm not up on the math behind it. Water flow is the pivotal bit of the equation. With a high flow filter, you're going to need a way to slow it down inside the reactor without impacting your flow rate too much. Tube diameter helps with that.


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## Ahura-sama (Dec 7, 2009)

Put a bioball in the chamber. It'll help trap the smaller bubbles from being taken-in to the flow.

You could also fill the entire length of the reactor w/ bio-balls. This will trap even big bubbles that form from merging of the smaller ones. However know that this will retard your outflow significantly. So unless you have powerful flow to compensate I wouldnt recommend it.

Elbow also reduce the flow.

If this is your first time, personally, you better off buying one from others. You will save at least 5-10 bucks in time and parts. Also the pvc cement is not pleasant to deal w/. It's horrible as a matter of fact.

9 bio ball or just one, 20 shipped. Buy it :V


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## Loop (Jan 8, 2011)

Ahura-sama said:


> If this is your first time, personally, you better off buying one from others. You will save at least 5-10 bucks in time and parts. Also the pvc cement is not pleasant to deal w/. It's horrible as a matter of fact.
> 
> 9 bio ball or just one, 20 shipped. Buy it :V


I don't know about that. I usually do everything 100% right on the first try every time.:icon_mrgr Thanks for the offer to buy, but I want to make it for fun also. I enjoy the DIY part, not just trying to save money.





I do have another question though. Do you guys get alot of splashing, or waterfall sound from these? I 'm a little worried I'm going to be wasting my efforts to make something that drives me crazy to listen to all the time.


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## waters10 (Oct 22, 2008)

It's about the water velocity going through the reactor.

You asked what happens when the water goes from the small canister tubing to the large PVC pipe. The flow rate remains the same, but since the cross sectional area is different, the velocity goes down. Just like the Amazon river moves a ton of water, but at slow speeds, since it's a very wide river. In the reactor it'll be this velocity against the bubbles buoyancy forcing them up.

So PVC diameter matters, because at the same flow rate, velocity will decrease as the diameter increases.

Bubble size matters, cause bigger ones have greater buoyancy, like stated before.

Length of reactor matters, cause the longer it is, more space for the bubbles to fight the water flow and get dissolved. If if it's too short, the water might have enough velocity to carry the bubbles to the tank.

I think the key is to start with your filter flow rate and search for similar designs that work with that flow rate. If you're using a filter with a high flow rate, you might want to split the flow before the reactor, because the velocity reduction you get from the bigger PVC diameter might not be enough and you'll see bubbles being blown in your tank.


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## mott (Nov 23, 2006)

You will get some splashing sounds, but I can't hear mine with the cabinet doors closed.
Stay away from elbows you will get better flow with smooth curves of your canister tubes.
You should also add a relief valve for gas build up inside the reactor, my aqua medic 1000 has one and it comes in handy.
I would think that if you had the inline difuser before the reactor it should work. Think about it, the bubbles are already tiny, when they enter the reactor they should dissolve pretty quick because of the violent swishing inside the chamber imo. Don't know for sure but it seems like it would work.
Good luck!


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## Loop (Jan 8, 2011)

mott said:


> I would think that if you had the inline difuser before the reactor it should work. Think about it, the bubbles are already tiny, when they enter the reactor they should dissolve pretty quick because of the violent swishing inside the chamber imo. Don't know for sure but it seems like it would work.
> Good luck!


That was my original thought, but the points made above make sense to me also. I figured I might as well try it since it's already in the lines. Never gonna know for sure if I don't try. If I'm getting a bunch of bubbles still I'll just disconnect it and try with just the reactor. No big deal.


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## kevmo911 (Sep 24, 2010)

I feel like I read Dave-H tried something like that, and the already-diffused microbubbles didn't get absorbed. Too light, possibly.


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## farebox (Oct 21, 2006)

*Rex Griggs Reactor*

Just like to say that I had Rex build me one for my 55GA planted tank three yrs. ago, working just fine. Keep it simple guys, why worry about all the science and math! My drop checker stays green......
farebox


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## Loop (Jan 8, 2011)

farebox said:


> why worry about all the science and math!


Because I can never leave anything alone. Sorta like Tim Taylor, I feel like anything can be improved and that I'm the person to do it, even when I'm grossly unqualified and incapable

But also, I just like to understand how things work, and make things myself whenever possible.


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## Hannothan (Dec 26, 2010)

mott said:


> Stay away from elbows you will get better flow with smooth curves of your canister tubes.


I tried this. Short of screwing the reactor to the wall, I couldn't get it situated right where the hose wouldn't crimp. Crimped hose is much worse than an elbow, so I put on elbows.

The nice thing about the threaded reducer bushings is that you can mix, match, or swap out what ever you need.


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## Hannothan (Dec 26, 2010)

farebox said:


> Just like to say that I had Rex build me one for my 55GA planted tank three yrs. ago, working just fine. Keep it simple guys, why worry about all the science and math! My drop checker stays green......
> farebox


Science is the foundation of the planted aquarium! And math is the foundation of all science! :biggrin:


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