# Ideas why Rex Grigg reactor isn't dissolving CO2 efficiently?



## burr740 (Feb 19, 2014)

Supa Mint said:


> would some back pressure, via an adjustable valve on the output side of the reactor help the CO2 dissolve in the water?


Not sure it will solve the entire problem but yes, this will help a lot.


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## Craigthor (Sep 9, 2007)

Possible reactor is too short for the flow so you get the buildup at the top.


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## Immortal1 (Feb 18, 2015)

Another possible issue might be your mounting location of the reactor. Ideally you would want the output of the reactor (the bottom) to be as low as possible - preferably just as low as the bottom of the canister filter. What this does is use the water column head pressure to it's fullest extent to increase the pressure inside the reactor to squeeze the co2 bubbles (but does not slow down canister flow). Putting a valve on the output of the reactor also adds pressure to the inside of the reactor (same effect) but does slow down your flow.


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## PlantedRich (Jul 21, 2010)

Is there still room for expressing different views in the current toxic environment?

Some thoughts on different ideas to start. Water pressure increases about .4 to .5 PSI for foot of height. So moving the reactor even six feet will change the pressure less than 3 PSI. That's not going to make much difference is it? 
If the CO2 is leaving the reactor, it is going into the water so you are likely to be getting more in. Mag drive filter pumps generate almost no measurable PSI. I might guess less than 1PSI, so using a restriction will only cut the flow. Even algae in the tubing is enough to cut filter flow. 

Some things that I see may happen without you thinking about them. One is that the point where the CO2 enters probably changed and it is probably not getting to the drop check in the same way. 
Things I would check are how the water circulates and where the two items are located. If the drop check was reading near the former point like maybe above it and it is now across the tank and the CO2 is coming in at the top like through a spraybar, the reading will be different. You may find running the return filter flow down to near the bottom will get more CO to stay in the water. 
I no longer use spraybars with CO2 as it blows too much back into the air. I use powerheads to maintain surface movement.


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## Supa Mint (Jul 5, 2016)

burr740 said:


> Not sure it will solve the entire problem but yes, this will help a lot.


Thanks - adding some backpressure will probably be my next attempt to improve the dissolving of CO2.



Craigthor said:


> Possible reactor is too short for the flow so you get the buildup at the top.


The reactor is 20" long. The CO2 buildup eventually resolves itself after the solenoid (and light) shuts off for the night - which means that I'm probably dosing (undissolved) CO2 for longer than necessary. 
Do you think that the gas layer buildup makes CO2 dissolving less efficient? Gas (CO2) is much more compressible than liquid (H2O), so a CO2 layer wouldn't have the 'force' to dissolve.
Do you think that reducing the water flow rate (it's adjustable) would improve the CO2 dissolving? Or would this just allow for an even larger gas layer? Plus, I would hate to reduce filtration (flow) unless necessary.



Immortal1 said:


> Another possible issue might be your mounting location of the reactor. Ideally you would want the output of the reactor (the bottom) to be as low as possible - preferably just as low as the bottom of the canister filter. What this does is use the water column head pressure to it's fullest extent to increase the pressure inside the reactor to squeeze the co2 bubbles (but does not slow down canister flow). Putting a valve on the output of the reactor also adds pressure to the inside of the reactor (same effect) but does slow down your flow.


Thanks, I see your point. However, the reactor output (and the cannister filter) is on the floor. So, unfortunately, I can't add additional pressure by lowering any further.



PlantedRich said:


> .... Some things that I see may happen without you thinking about them. One is that the point where the CO2 enters probably changed and it is probably not getting to the drop check in the same way.
> Things I would check are how the water circulates and where the two items are located. If the drop check was reading near the former point like maybe above it and it is now across the tank and the CO2 is coming in at the top like through a spraybar, the reading will be different. You may find running the return filter flow down to near the bottom will get more CO to stay in the water.
> I no longer use spraybars with CO2 as it blows too much back into the air. I use powerheads to maintain surface movement.


Ok, these are interesting points - thank you.
1. Location of drop checker and spray bar are the same as previous (although the flow/circulation rate could be slightly different now).
2. Generally, I feel that circulation is 'decent' and CO2 loss at surface is minimal: 275gph in 29 gallon tank; spray bar mounted vertically; almost no surface agitation (bad for fish); plants all swaying (I've struggled to keep plants from blowing over by deflecting/angling spray bar into back glass).
3. Filter return flow at bottom (corner)

This all leads me to believe that my previous CO2 readings with the inline filter (and with lots of micro-CO2 bubbles) were falsely elevated by bubbles getting under the drop checker. But I still can't figure out why I can't get the drop checker to crack 30ppm with such a high bps rate.


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## PlantedRich (Jul 21, 2010)

The devil is often in the details? It may take a bit to get figured what is happening. 

Meanwhile there is another current post that somewhat shows what I find on the pressure in reactors. 
http://www.plantedtank.net/forums/9-equipment/1119826-need-reactor-advice.html

With the very short water column and a very tiny, weak mag drive motor, we not have enough pressure to measure as is shown in that post. there is some pressure there but likely just not enough to measure and show on a meter reading 0-100. I have no idea how much increase in pressure we might need but then I find it hard to figure how to get that pressure increase when talking about a plastic pipe with plastic tubing which is almost a basic open at both ends. 
Seems to me that we would need to cork up both ends of the tubing to get any real pressure in the reactor. 

When I think of building pressure in a reactor, I think of trying to blow up an air mattress with a hole in it!


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## burr740 (Feb 19, 2014)

Anyone who doesnt believe restricting the outflow, even a little bit, can increase the pressure enough to make a HUGE difference in the final dissolution of tiny micro bubbles..... has never tried it for themselves.


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## milesm (Apr 4, 2006)

you said that the flow rate/circulation pattern could be different than what it was before. many report reduced flow rates when going through a reactor. these changes could account for your current lower co2 levels, especially if spraybar and drop checker are in the same location. 

i think your drop checker overestimated co2. as you said, the mist from the atomic was driving it green which means that you had less than 30ppm co2. at 2bps on a 29g, i'm almost certain it was indeed, less than 30.

you could also try turning co2 on an hour or two before lights on, and turn it off an hour or so before lights off.

how was plant growth using the atomic? what do plants look like with the reactor so far?


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## Supa Mint (Jul 5, 2016)

PlantedRich said:


> ....When I think of building pressure in a reactor, I think of trying to blow up an air mattress with a hole in it!





burr740 said:


> Anyone who doesnt believe restricting the outflow, even a little bit, can increase the pressure enough to make a HUGE difference in the final dissolution of tiny micro bubbles..... has never tried it for themselves.


Ok, I have just started an experiment to test an increase in back pressure. I have used a vise-clamp to pinch/flatten the tubing after the reactor. This is a very unscientific study, since I have no way to know the volume reduction or pressure increase (if any). But if the drop checker indicates an increase in CO2, then I can conclude that my cannister filter can handle some back pressure; and that dissolved CO2 is increased with back pressure.



milesm said:


> ....you could also try turning co2 on an hour or two before lights on, and turn it off an hour or so before lights off.
> 
> how was plant growth using the atomic? what do plants look like with the reactor so far?


Thanks, I currently turn the CO2 on 1 hour before lights; and off 30 minutes before dark. I just can't quite get the drop checker to hit desired 30ppm of CO2, regardless of how long CO2 is on, or at any bps.

I hesitate to compare the plant growth with the inline diffuser to the reactor, since I changed fertilizer strategy to EI at the same time. But plant growth appears to be better; and algae growth has possibly decreased. I just can't seem to get the CO2 level increased to the level that I desire (>30ppm).


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## PlantedRich (Jul 21, 2010)

I feel a restriction on the outflow will change the amount of bubbles seen coming out. However, I do not agree that this is caused by an increase in pressure but I feel it is far more likely to be the reduced flow making the contact time much more. I fully agree that I have not used any form of flow restriction but when I did get some bubbles escaping, I did not want to reduce flow as I want my filters to perform as well as possible. 
I found that creating a longer dwell time inside the reactor by increasing either the length or diameter of the PVC worked to remove the bubbles without cutting the flow. 
My basic thought is that we do know that CO2 will move into the water when given time. That is the whole idea of both the Cerge's and the Grigg's. I also see the other post which shows there is no measurable pressure inside the reactor as the poster has it. So does anybody have a meter or other info showing us how this pressure is developed when the system is open to the tank water at both ends? I see no reason for much increased pressure but I do see there will be less flow. Less flow gives longer time for the CO2 to move into the water. This is one of the variables that I try to estimate when I build a reactor for a different size tank or filter. I find I have to size the reactor to fit both the flow from the filter and the amount of CO2 I expect to push into the tank. When I get it wrong, I cut the PVC and add a couple more inches to the length but I do not ever want to restrict the flow. 
I'm willing to change my mind if there is somebody with a meter on their system and they can show a pressure increase by reducing flow.


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## burr740 (Feb 19, 2014)

PlantedRich said:


> I feel a restriction on the outflow will change the amount of bubbles seen coming out. However, I do not agree that this is caused by an increase in pressure but I feel it is far more likely to be the reduced flow making the contact time much more. I fully agree that I have not used any form of flow restriction but when I did get some bubbles escaping, I did not want to reduce flow as I want my filters to perform as well as possible.
> I found that creating a longer dwell time inside the reactor by increasing either the length or diameter of the PVC worked to remove the bubbles without cutting the flow.
> My basic thought is that we do know that CO2 will move into the water when given time. That is the whole idea of both the Cerge's and the Grigg's. I also see the other post which shows there is no measurable pressure inside the reactor as the poster has it. So does anybody have a meter or other info showing us how this pressure is developed when the system is open to the tank water at both ends? I see no reason for much increased pressure but I do see there will be less flow. Less flow gives longer time for the CO2 to move into the water. This is one of the variables that I try to estimate when I build a reactor for a different size tank or filter. I find I have to size the reactor to fit both the flow from the filter and the amount of CO2 I expect to push into the tank. When I get it wrong, I cut the PVC and add a couple more inches to the length but I do not ever want to restrict the flow.
> I'm willing to change my mind if there is somebody with a meter on their system and they can show a pressure increase by reducing flow.


If it was solely due to increased dwell time then cutting the flow before the reactor would have the exact same effect. 

It'd be an easy test with a pair of vise grips. Partially crimp the hose down before the reactor and see how much co2 it can handle. Then do the same thing after the reactor and compare.


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## Supa Mint (Jul 5, 2016)

Supa Mint said:


> Ok, I have just started an experiment to test an increase in back pressure. I have used a vise-clamp to pinch/flatten the tubing after the reactor. This is a very unscientific study, since I have no way to know the volume reduction or pressure increase (if any). But if the drop checker indicates an increase in CO2, then I can conclude that my cannister filter can handle some back pressure; and that dissolved CO2 is increased with back pressure.


Surprising results from my first back pressure experiment: The sound of the gas/liquid layer within the reactor disappeared; and I still did not observe any CO2 bubbles in the aquarium. However, there was no observable difference in the color of the drop checker!

So I'm still completely baffled as to where my CO2 is going!

I believe that the drop checker is performing correctly, since I could get it turn yellow when using an in-line diffuser (with lots of micro-bubbles); and because it also turns yellow when exposed to air (during water changes).

As stated previously, I do not know where I could be losing CO2 - no bubbles in tank, minimal surface agitation, and no observable CO2 leaks.

For next steps, I can think of trying the following:
1. Reduce adjustable flow rate of canister filter - while this may increase dwell time, I wonder if the gas/liquid layer in the reactor will become larger.
2. Increase the CO2 delivery rate - at >10bps, and a gas/liquid layer forming in the reactor, I feel that I'm already at an excessive CO2 delivery rate for my water flow rate; however, I'm running out of ideas.
3. Install inline diffuser before the reactor (and capping CO2 inlet port of reactor) - thinking that delivering micro-CO2 bubbles (rather than large bubbles) to the reactor may help with dissolving the CO2.

Any thoughts or suggestions would be very welcome!

- Erick


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## burr740 (Feb 19, 2014)

I'd toss the drop checker, they're only rough guess under the best of circumstances. Too much room for error.

Better to do a relative PH test between degassed tank water and the tank with the co2 on. There should be a full 1.0 drop, minimum, preferably by the time the lights come on, or shortly thereafter.

You'll need a digital PH pen to do this, cant use drop tests or strips. They're about 15-20 bucks on amazon, and you'll need some 7.0 calibration solution. It's the best investment you can make at this point.

Side note:
Here's an interesting vid where a guy with a cerges fixed a problem by adding more pressure. The pressure discussion starts around the 3 min mark

https://www.youtube.com/watch?v=Itj-qxlKmIo


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## natemcnutty (May 26, 2016)

Have you tried reaching out to Colin about this yet? I'm building my own reactor this weekend powered by a 2215. I'll see if I can replicate your issue and play with length and diameter to see what makes a difference 

Sent from my Nexus 6 using Tapatalk


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## NickRummy (Feb 27, 2012)

I'm going to chime in just because we have similar setups and I'm just getting back into this and I've noticed a few things on my setup recently. I'm running a 29G with a Marineland C-220 (220gph) and a Koralia 240 powerhead on during the day. 

What pressure is your CO2 being injected at? I've attached a photo of my setup. When I first built a few years ago (I didn't use it for a while and just started it back up a few days ago). I added a pressure gauge to the top of my reactor in hopes of seeing pressure but like noted in this thread there isn't enough to measure on a 0-100 scale. Wondering if there might be other gauges out there that could? I have a valve on the output of my reactor but I run it wide open. I haven't had any issues with bubbles getting into the display tank yet.

Could it be possible there is oxygen in the top of the reactor and it's just sitting there? I added a valve into the top of my reactor (see the tube coming off it) so that when I do cleaning and refill with water I can purge any air out. 

One thing I noticed yesterday was that I would randomly get the air noise in the reactor too. I can only run my CO2 at around 20psi (Red Sea regulator) right now and I'm noticing that water actually goes into the CO2 tube and then eventually the CO2 pushes back into the reactor. I'm not running a backflow valve though so I'm sure that's half the reason. I have a GLA system coming I'm swapping to. I just added a drop checker the other day and it's still showing low CO2. I don't have many plants and I'm trying to start out slow so I'm running around 1.5bps and slowly bringing it up until I get what I want. 

I also have an RKE system coming with a PH probe that I'm hoping will help with CO2 amounts.


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## PlantedRich (Jul 21, 2010)

Another thought might be that the reactor is okay. Colin has a habit of building/selling good stuff so I would be reluctant to mod it until I really understood it totally. 
No idea on how you operate, so I don't want this to sound like pointing a finger? But tis there a chance that the way you are restating the canister needs some change. Possible that you need to tilt the reactor on restarts so that the air is not trapped in it? 
I have reactors in a number of different setups and find there is a difference in the way they need to operate. When the reactor sets on the floor next to the canister, I need to leave it loose so that I can swing the base up to drain the air out to get a good restart after filter cleaning. 
Any possibility that much of the bubbles and noise in not from CO2, but simple trapped air? Maybe an easy , low level test would be to tip the base of the reactor so that any trapped air will pass through and see how it changes things? 
I'm told by high level thinkers that this doesn't happen but then they are not at my tank when they say that~!


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## NickRummy (Feb 27, 2012)

Found this for a gauge that should read the pressure, but it's not cheap. Don't think you really get anything out of know the pressure either since it's so minimal. Makes me wonder if the pressure would show up though. haha

https://www.amazon.com/Kodiak-Contr...1486134410&sr=8-5&keywords=low+pressure+gauge


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## RobnSonji (Oct 6, 2013)

burr740 said:


> I'd toss the drop checker, they're only rough guess under the best of circumstances. Too much room for error.
> 
> Better to do a relative PH test between degassed tank water and the tank with the co2 on. There should be a full 1.0 drop, minimum, preferably by the time the lights come on, or shortly thereafter.
> 
> ...



After watching the video.... It looks like increasing the pressure on the inlet side did help?
He increased pressure on the in side by using 2 canisters plumbed together. Am I understanding that correctly?
If you dont have enough water flow to keep the bubbles churning they build up at the top to form one large bubble that does not have enough contact with the water to dissolve.

It leaves me with the impression that you need enough water flow to keep the bubbles churning and not building up at the top.....and....enough dwell time for the bubbles to dissolve.


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## PlantedRich (Jul 21, 2010)

When thinking further, we all have a gauge on our reactor pressure but just don't think of it that way. We use the reg to set the working pressure going into the reactor and the pressure is the same at the reg as at the reactor. So to find what pressure is in that line, we can watch the bubble count and when we turn the working pressure down to the point that bubbles neither enter nor water come out, we are close to the reactor pressure? 
Critics might point out that this ignores the "friction" of the tubing, etc., etc. but I'm not speaking rocket science.


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## natemcnutty (May 26, 2016)

I'm curious, if the CO2 is able to rise fast enough to escape the flow and build up at the top, does that not mean the flow is too slow? I'm pretty sure he uses 2" pipe, and at 20" long, is it possible the head pressure is slowing down flow too much and allowing the CO2 to rise faster than the flow going through?

I know those things are usually built for 55 gallon+ size tanks with 500gph canisters. Personally, I'd try to get my hands on a higher gph powerhead and try it outside of the canister filter loop.

Sent from my Nexus 6 using Tapatalk


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## milesm (Apr 4, 2006)

burr740 said:


> I'd toss the drop checker, they're only rough guess under the best of circumstances. Too much room for error.
> 
> Better to do a relative PH test between degassed tank water and the tank with the co2 on. There should be a full 1.0 drop, minimum, preferably by the time the lights come on, or shortly thereafter.
> 
> ...


+1. but i think you can get by with api pH test kits.


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## NickRummy (Feb 27, 2012)

The video is interesting. Is that about how much CO2 you guys have entering your reactor? Mine isn't near that but i'm also not up to correct levels yet either. Looks like a ton of CO2 being dumped in there.


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## Supa Mint (Jul 5, 2016)

burr740 said:


> I'd toss the drop checker, they're only rough guess under the best of circumstances. Too much room for error.
> 
> Better to do a relative PH test between degassed tank water and the tank with the co2 on. There should be a full 1.0 drop, minimum, preferably by the time the lights come on, or shortly thereafter....


Thanks, I'm looking to acquire a pH meter. My pH with no CO2 is 6.8 (well, at least as measure by the API kit), so if I'm understanding correctly, I'd want my pH to drop to 5.8? Yikes - that seems low!



natemcnutty said:


> Have you tried reaching out to Colin about this yet? I'm building my own reactor this weekend powered by a 2215. I'll see if I can replicate your issue and play with length and diameter to see what makes a difference


Yes, Colin has been great, and has been very supportive with troubleshooting ideas.



NickRummy said:


> I'm going to chime in just because we have similar setups and I'm just getting back into this and I've noticed a few things on my setup recently.... What pressure is your CO2 being injected at? .... Could it be possible there is oxygen in the top of the reactor and it's just sitting there? I added a valve into the top of my reactor (see the tube coming off it) so that when I do cleaning and refill with water I can purge any air out.
> 
> One thing I noticed yesterday was that I would randomly get the air noise in the reactor too. I can only run my CO2 at around 20psi (Red Sea regulator) right now and I'm noticing that water actually goes into the CO2 tube and then eventually the CO2 pushes back into the reactor. I'm not running a backflow valve though so I'm sure that's half the reason. I have a GLA system coming I'm swapping to. I just added a drop checker the other day and it's still showing low CO2. I don't have many plants and I'm trying to start out slow so I'm running around 1.5bps and slowly bringing it up until I get what I want.
> 
> I also have an RKE system coming with a PH probe that I'm hoping will help with CO2 amounts.


Thanks, it will be great to compare to your setup...
- My regulator is set to 35psi, which is obviously way more than I need to push CO2 into the reactor. 
- I doubt that it is oxygen at the top of the reactor, because the gas/liquid layer only occurs as I'm adding CO2; and disappears after my CO2 shuts off. I'm not sure where the oxygen/air would be coming from. 
- I currently use a GLA regulator, and added a check valve in the CO2 line.
- An RKE pH controller would be awesome... maybe some day!



PlantedRich said:


> Another thought might be that the reactor is okay. Colin has a habit of building/selling good stuff so I would be reluctant to mod it until I really understood it totally.
> No idea on how you operate, so I don't want this to sound like pointing a finger? But tis there a chance that the way you are restating the canister needs some change. Possible that you need to tilt the reactor on restarts so that the air is not trapped in it?
> I have reactors in a number of different setups and find there is a difference in the way they need to operate. When the reactor sets on the floor next to the canister, I need to leave it loose so that I can swing the base up to drain the air out to get a good restart after filter cleaning.
> Any possibility that much of the bubbles and noise in not from CO2, but simple trapped air? Maybe an easy , low level test would be to tip the base of the reactor so that any trapped air will pass through and see how it changes things?
> I'm told by high level thinkers that this doesn't happen but then they are not at my tank when they say that~!


Fair questions - thanks for checking. I have the reactor velcro'd to the cabinet, so I could easily rotate it. If I got air in it, this would be an easy way to do it. But I don't believe that I am introducing air into the reactor because the inlet sits at the bottom of the tank, and I never reach that point during water changes (plus, I shut off the canister filter flow during w/c). Also, it is pretty clear that the sound of the gas/liquid layer starts shortly after CO2 starts and gets progressively louder until the CO2 shuts, and then it gets progressively quieter until it becomes silent - supposedly as CO2 gets fully dissolved in the reactor. During operation with no CO2 being added, the reactor is silent.



NickRummy said:


> The video is interesting. Is that about how much CO2 you guys have entering your reactor? Mine isn't near that but i'm also not up to correct levels yet either. Looks like a ton of CO2 being dumped in there.


I'm not able to see inside of my reactor, but at 10-20 bps, I'd expect that it would look similar to that.


*THANK YOU EVERYONE FOR HELPING ME TROUBLESHOOT THIS!!!*

-Erick


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## NickRummy (Feb 27, 2012)

I was just playing with the CO2 flow. Up around 10bps (i'm guessing, too fast to really count) I certainly get a air sound in the reactor and start getting small bubbles in the output and in the display tank. My reactor is a LOT shorter than the one in the video. I may throw some media balls in there to help break up the bubbles and keep them from flowing to the bottom of the reactor so easily.


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## PlantedRich (Jul 21, 2010)

NickRummy said:


> I was just playing with the CO2 flow. Up around 10bps (i'm guessing, too fast to really count) I certainly get a air sound in the reactor and start getting small bubbles in the output and in the display tank. My reactor is a LOT shorter than the one in the video. I may throw some media balls in there to help break up the bubbles and keep them from flowing to the bottom of the reactor so easily.


This is a point where I begin to disagree with some of the thinking on modding the original design. I see a lot of mods being made but I also see a lot of folks who have not followed the original and complain that they have problems. 
I fully understand the desire to improve things but when things get worse, it seems we should question the last improvement rather than the original design. What I'm saying is it seems unfair to go on forums to complain that the Grigg's, Cerge's, etc. is not a good reactor if we have changed it. 
I feel adding bio-balls or anything inside the tube is one mod that has potential for fixing but it also has potential for adding trouble. I feel a better solution to fixing the problem of CO2 bubbles passing through, is to go back and look at how the design may be different from the original design and try to understand why it doesn't work for me. 
First question on bio-balls might be, how are you going to clean them when they get full of gunk and the flow stops? Anybody using a canister for long will see gunk collecting in the simple walls of the tubing so I can only guess what is happening on bio-balls? 
When I have built Grigg's style reactors, I have also made some changes but only minor ones where I am willing to accept that I will lose some flow. Adding elbows and setting it on the floor for instance. When I find it is passing bubbles through, I do not want to reduce my precious flow through my filter so I go for simple fixes like adding 2,4 or even 6 inches of pipe. 
I find the amount of time the water and CO2 are together is what controls how many bubbles are blown out into my tank. 
When bubbles show in my tank, I increase the amount of space the bubbles have to pass through before leaving the reactor but I want the water to move through as quickly as the filter can push it. 
A simple solution might be to cut the PVC, add two couplings and a couple more inches of pipe?


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## Immortal1 (Feb 18, 2015)

Been following this thread and all the good advice that is being offered. One thing I can add is this "First question on bio-balls might be, how are you going to clean them when they get full of gunk and the flow stops? Anybody using a canister for long will see gunk collecting in the simple walls of the tubing so I can only guess what is happening on bio-balls?" About 1 month ago I added a section of course sponge to my Cerges reactor (for what ever reason). As my canister filter got dirty, the dirt collected in this sponge. Yesterday I took the Cerges apart as I got tired of the crap floating around in my tank. Seems my Cerges was the source of all that crap. 

Long story short, I would avoid putting bioballs or course foam in your _______ reactor unless you plan on cleaning the reactor on a regular basis. I did NOT find that the course sponge helped with dissolving the co2.


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## NickRummy (Feb 27, 2012)

Good enough info for me to pass on the bioballs. Haha I was going to try it because it was an easy thing to do without much commitment. 

Does anyone run their reactor on it's own pump? Like a small mag drive plumbed externally inline? Guess it adds more plumbing and intake output in the tank but you would have more control over it and it wouldn't change your filtration at all?


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## NickRummy (Feb 27, 2012)

I will say I throttled back the output on the reactor and this helped with dissolving the bubbles and stopped the bubbles in the tank but like you said it slows down my filtration.


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## milesm (Apr 4, 2006)

NickRummy said:


> Does anyone run their reactor on it's own pump? Like a small mag drive plumbed externally inline? Guess it adds more plumbing and intake output in the tank but you would have more control over it and it wouldn't change your filtration at all?


i have mine (unmodified, exactly as shown on rex's page, just a little shorter) on a closed loop with an external powerhead. true, couple more stuff in the tank, but you have better control, not affected by declining filter output, and provides more circulation. only way to use a reactor, imo.


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## PlantedRich (Jul 21, 2010)

NickRummy said:


> I will say I throttled back the output on the reactor and this helped with dissolving the bubbles and stopped the bubbles in the tank but like you said it slows down my filtration.


Curious minds want to know? When you say you throttled back the output, did you do it by putting a restriction on the output side of the reactor or by restricting the flow between the canister and reactor. That gets back to whether the bubbles coming out is changed by the flow reduction if it is on the input to the reactor but would still leave open the question of pressure change if the restriction is on the output side. 

We sometimes get into confusion on reactors when we think of Cerge's and Grigg's as being the same. Some points, they are but when it comes to some of the details, there is a lot of difference. Can one simply unscrew the Cerge's filter housing? I'm not into using them so that would be one thing that would change my thoughts on adding bio-balls. If one could unscrew and remove them, I would find them less a problem than if one has to take the whole reactor out of service, cut the pipe and glue back. The wait time for the new solvent to clear would be enough to make me pause.


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## NickRummy (Feb 27, 2012)

I have a ball valve on the output of the reactor. I don't think its the flow that changes the bubbles disolving because when I restricted the flow the bubbles in the reactor went away. If it was just the flow change I think the bubbles would still be there just not moving around as much right?

This is a cerges and yes the lower portion of the canister just unscrews. It has an o-ring seal. You could drop the bio balls in and reattach it and turn it back on in a few minutes.


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## Supa Mint (Jul 5, 2016)

Hi Everyone,

Just a quick update: I have a Pinpoint pH meter on the way. I will take accurate measurements of pH of different scenarios, to possibly help understand how much CO2 is dissolving:
1. Normal water flow rate through reactor
2. Normal water flow rate through reactor with back pressure added
3. Reduced water flow rate through reactor
4. Same CO2 bps through inline filter (no reactor)

Results to follow.


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## PlantedRich (Jul 21, 2010)

Supa Mint said:


> Hi Everyone,
> 
> Just a quick update: I have a Pinpoint pH meter on the way. I will take accurate measurements of pH of different scenarios, to possibly help understand how much CO2 is dissolving:
> 1. Normal water flow rate through reactor
> ...


Sounds like a logical way to test with some caution. I might throw in that there may be some confusion for some of the readers as to how flow and back pressure are related. 
As listed, I should think item 2 and 3 are going to be related, depending on how the flow is reduced. With increased back [pressure flow will also be reduced so what might happen is that as the flow is reduced when we add back pressure we might jump to the conclusion that the pressure is what's needed but simply reducing flow may get the same thing. One way we often see back pressure increased is by adding more height (head ) to the output. But that also comes with decreased flow. 
My point is that I agree that increased pressure from 10PSI to 50PSI might change the bubble question but I don't see any way that we will have much pressure in a reactor as long as water can flow through. I'm able to push CO2 into my reactors down to below 4PSI and my reg meters get pretty questionable below that. I can't see any way to make a really significant change in the pressure when we are talking about a reactor that has water flow in and out at each end as well as plastic tubing feeding the CO2. I don't think a change in pressure from something like 2.0 PSI to 2.8 PSI will effect much.


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## Supa Mint (Jul 5, 2016)

PlantedRich said:


> Sounds like a logical way to test with some caution. I might throw in that there may be some confusion for some of the readers as to how flow and back pressure are related.
> As listed, I should think item 2 and 3 are going to be related, depending on how the flow is reduced. With increased back [pressure flow will also be reduced so what might happen is that as the flow is reduced when we add back pressure we might jump to the conclusion that the pressure is what's needed but simply reducing flow may get the same thing. One way we often see back pressure increased is by adding more height (head ) to the output. But that also comes with decreased flow.
> My point is that I agree that increased pressure from 10PSI to 50PSI might change the bubble question but I don't see any way that we will have much pressure in a reactor as long as water can flow through. I'm able to push CO2 into my reactors down to below 4PSI and my reg meters get pretty questionable below that. I can't see any way to make a really significant change in the pressure when we are talking about a reactor that has water flow in and out at each end as well as plastic tubing feeding the CO2. I don't think a change in pressure from something like 2.0 PSI to 2.8 PSI will effect much.


Yes, these are good points. Here's a verbiage modification to the list of experiments:
1. Normal water flow rate through reactor
2. Reduced water flow rate through reactor via added back pressure
3. Reduced water flow rate into reactor without added back pressure (adjustable flow canister filter)
4. Same CO2 bps through inline filter (no reactor)


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## burr740 (Feb 19, 2014)

PlantedRich said:


> Sounds like a logical way to test with some caution. I might throw in that there may be some confusion for some of the readers as to how flow and back pressure are related.
> As listed, I should think item 2 and 3 are going to be related, depending on how the flow is reduced. With increased back [pressure flow will also be reduced so what might happen is that as the flow is reduced when we add back pressure we might jump to the conclusion that the pressure is what's needed but simply reducing flow may get the same thing. One way we often see back pressure increased is by adding more height (head ) to the output. But that also comes with decreased flow.
> My point is that I agree that increased pressure from 10PSI to 50PSI might change the bubble question but I don't see any way that we will have much pressure in a reactor as long as water can flow through. I'm able to push CO2 into my reactors down to below 4PSI and my reg meters get pretty questionable below that. I can't see any way to make a really significant change in the pressure when we are talking about a reactor that has water flow in and out at each end as well as plastic tubing feeding the CO2. I don't think a change in pressure from something like 2.0 PSI to 2.8 PSI will effect much.


OK I have a question. When I put a ball valve after the reactor, close it down just a little bit (because it only takes a little to make a big difference) you say the improvement comes from increased dwell time, nothing to do with pressure.

You may be right?

But my question is how much would you say dwell time really increases in the above scenario? Say closing the valve 20%. 

And how much longer would bubbles need to be retained to make a difference? 5 more seconds, 30 seconds, 10 minutes?

Personally I cant see the dwell time going up enough to make any difference. Ever seen a micro bubble floating around in the tank? Did it ever disappear before your eyes?

I have the same opinion about your dwell time theory as you have regarding the increased pressure theory - that closing the valve as we're talking about here, isnt going to cause dwell time to go up enough to make much difference.

What are your thoughts on that?


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## PlantedRich (Jul 21, 2010)

Since the bubbles are working too flow up, as the flow decrease, the velocity/speed of the water decreases. So a bubble that might be blown out at one speed may turn around and flow back up several times at a slower speed. I see the bubbles as being much like a hailstone in reverse. The difference in the size of a hailstone is increased a great deal when the speed of the updraft that keeps it suspended changes. 
I don't see it as simply the bubble taking X seconds to move from one end of the reactor to the other but that it may make several up/down cycles and all the time gradually getting smaller until it is too small to float. One of the reasons Grigg's used his method of adding the CO2 through an undersized hole was to let the bubble out in the faster center portion of the water flow. This helps to keep the bubble from entering along the side of the reactor where there is less flow which may let it float to the top and collect to make noise. 
Spent any time teaching kids how to drop boats into the creek? 
I get this idea from watching things floating in water like streams. A leaf that falls into fast water will go from one end of a pool to the other quickly but if it falls into slower/wider water, it may circle many times before reaching the far end. 
Leaves don't get smaller so it is not totally the same, of course. 
I feel it takes a balance of where the CO2 enters so that it meets a good flow that won't let it collect but also not such a fast flow that the bubble is simply carried out the far end. I want it to float up, ix and get smaller until finally it is too small to float and becomes part of the water.


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## burr740 (Feb 19, 2014)

Once the bubbles reach micro size they dont have much buoyancy. This is where your theory falls apart (imo)

On the other hand, it takes very little very little added pressure to squeeze down an already tiny micro bubble. CO2 is "soft", not like air bubbles.

This is all happening in the lower region of the reactor, where the bubbles are micro size and agitation is lowest. These final micro bubbles arent swirling around up top, fighting to float up. They're down low at the mercy of the current.


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## Immortal1 (Feb 18, 2015)

I really don't have a good way to test my setup but if I could I would like to see how it compares to what @burr740 and @PlantedRich are discussing. 
On my Cerges reactor I have a by-pass valve, but no ball valve on the output side. I have found that closing the by-pass valve does seem to slow the water flow into my tank enough that I can visually tell the difference (pressure in the reactor may go up a bit due to the higher flow rate thru the reactor). But I can't say using that setting works any better (with regards to how quickly the co2 level in the tank drops).
When I set the bypass valve to say 60-65% (really just a guess - more than 50% but not really 75%) where 35-40% of the canister filter flow is allowed to bypass the Cerges the flow into my tank is more what I would call normal. If I open the bypass valve to 100%, the flow into my tank is basically the same. At this bypass setting, my Eheim Pro 4+ Model 350 connected to my Cerges reactor seems to take about 2 hours to give me about a 1 point pH drop using 20 psi cO2 and roughly 6-8 bps.

So, with all that said (sorry for so many words), I am really curious which is better for the Griggs / Cerges reactors - less overall water flow thru the reactor which gives more dwell time for the given amount of co2? Or, as an earlier video noted, crank up the volume of water going thru the reactor using a higher flow canister filter or even 2 canister filters "T'd' together to create as much water pressure as possible?

I am also curious if the diameter of the reactor to length ratio has any benefit? Cerges tend to be short and fat, Griggs tall and skinny (by comparison).

Will be curious to see what @Supa Mint comes up with


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## Remmy (Jan 10, 2007)

Any updates on this?
I have a rex grigg and im having troubles with inefficiency. Its at a point where i close the co2 2 hours before lights off and thats at around 3-4bps otherwise theres still gas churning inside after lights off.
If i run at a higher bubble rate it takes several hours for the gurgling sound to subside in the reactor... using a lightly stocked canister 325gph
reactor is 2" diameter and around 20" high


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## natemcnutty (May 26, 2016)

Remmy said:


> Any updates on this?
> I have a rex grigg and im having troubles with inefficiency. Its at a point where i close the co2 2 hours before lights off and thats at around 3-4bps otherwise theres still gas churning inside after lights off.
> If i run at a higher bubble rate it takes several hours for the gurgling sound to subside in the reactor... using a lightly stocked canister 325gph
> reactor is 2" diameter and around 20" high


Following the original design? Where and how are you joking up CO2? I've seen several modifications to the original design that I don't think work that well. Of course, this is just my opinion based on limited experience (only built 2 so far, but tried different mods my first time around).

First is the barbed fitting to hook the CO2 line up to. If you do this, you are now injecting against the wall rather than the center of the steam. Too much flow can make it even worse by pushing water down the center and back up the sides.

Second is a 90 degree elbow at the inlet. This seems to cause issues more often in lower flow where CO2 gets trapped up top and never really gets mixed back in.

I think the diameter and length need to be matched to the flow. The bypass mod can help make the reactor more tunable to your flow rate, but it does add quite a bit to the cost


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## Remmy (Jan 10, 2007)

natemcnutty said:


> Following the original design? Where and how are you joking up CO2? I've seen several modifications to the original design that I don't think work that well. Of course, this is just my opinion based on limited experience (only built 2 so far, but tried different mods my first time around).
> 
> First is the barbed fitting to hook the CO2 line up to. If you do this, you are now injecting against the wall rather than the center of the steam. Too much flow can make it even worse by pushing water down the center and back up the sides.
> 
> ...


Co2 getting trapped at the inlet could be happening, however i just tried tilting the reactor on its side enough that the tubing is higher than the inlet and no gas bubble was visible in the tubing
I think this suggests that the water pressure is able to push it down into the chamber and prevent it from rising to get stuck in that inlet elbow

Having said that i can't really think there is any other reasonable explanation, the canister flow should be adequate so i may just have to replace that elbow and see if it changes things... even though i dont really have room for a straight inlet


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