# Best CO2 Reactor/Diffuser



## coley24

I'm in the process of setting up a pressurized CO2 system for my 55 gal. planted tank. This is my first and I am looking for a little advice. What is the best way to effectively diffuse CO2 into the water with little waste? Would it be better to use a reactor or a diffuser? Which kind? Better to ask before purchasing...thanks for the help!

:fish1:


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## 1shooter

I started out with a glass difusser. After about 2 months I decided I wasn't getting enough co2 in my tank so I added a DIY reactor to out line on my canister.

Way better. Not only does work well. I was able to get rid of the ugly tube and difusser in my tank.

Cheap too!


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## Rex Grigg

I personally like reactors.

http://www.rexgrigg.com/diy-reactor.htm


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## coley24

Thanks for the replies, looks like I'll be setting up a reactor.
:fish1:


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## Jeff5614

Good choice. I've used them both and I just like the lower maintenance and less equipment in the tank that a reactor provides.


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## EdTheEdge

Reactors are great. I know this even though I've never used one. The main drawback of this type of reactor is that you can not see what is happening inside. For a newbie I'd be hesitant to advise using one. It would be more suited as a "next step". You can get plenty of CO2 in your tank using more traditional methods i.e glass diffusor, power head, etc. Not trying to discourage you but there is a learning curve when applying CO2. Start simple and learn, learn, learn.


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## coley24

Few more questions for you guys...
Is it worth it to cut up the hoses to either the intake or the outflow to my canister filter, or is it just as effective to use a powerhead? Also, any advice as to how to set up a bubble counter with this external reactor? It's very straightforward with the diffuser but here I don't see where there's a good flow rate to place it.


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## coley24

Scratch the bubble counter question, I've got that figured out.


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## FacePlanted

I just setup a Mazzei injector inline for my co2. It's awesome, and way better than the glass diffuser I had previously been using. When appropriately sized to your pump, they dont cause any noticible loss in flow. I'm never going back to anything else!


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## Rex Grigg

Most power heads will not work with a reactor as they don't have enough head in the pump to move the water out of the tank and back into the tank.

I'm a bit confused by EdTheEdge's comment. 

Why would you need to see what is happening inside? Water moves from top to bottom, gas is injected into the moving water column and tries to float to the top. The gas gets rolled around till it dissolves. 

You could build the reactor with clear PVC (and quadruple the cost if not more) but there is no real reason to do so. I have built over 100 of these reactors and there has yet to be a problem.


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## footbeat

FacePlanted: I remember reading that Mazzei works excellently, but one of the drawbacks is that it creates a haze of micro bubbles. I couldn't track down where I read this. Have you experienced this?


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## EdTheEdge

Rex

Not saying there is a problem with your design. Quite the contrary. It looks top notch. I was just saying that someone starting out with CO2 should probably start out simple. Too many high tech systems fail because of a lack of knowledge. 

Clear PVC would be better suited for a first reactor for someone new to CO2. That way one could see if too much CO2 was building up in the reactor among other things.....


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## coley24

Thanks for the replies. I bought the PVC pieces last night and have it mostly assembled, just the CO2 line in to finish. Rex, your instructions were great. 
:fish1:


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## CountViffer

*...to take this on slightly further...*

I'm about to build one myself, but I'm unsure as whether it's best to connnect a reactor to the inlet or outlet of the canister filter?

I've heard it said that the CO2 can deplete the oxygen levels in the canister, detrimentally affecting the biological filtration. Anyone know whether this is correct?

I think I'm going to run a second canister purely to power the CO2 and reactor, bearing in mind that this will also impove filtration,is it likely that I could have too much flow...is this a problem, and once again does running the reactor on the effluent side resolve the issue?

If it's better to use the effluent side then I'll have true redundancy in the filters ... which would be nice :icon_lol: .

Thanks.


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## coley24

I'm debating the same thing...on the output or the intake? I've heard on the output can reduce your flow by a good amount, is this true? I was planning on the intake but I'd hate to cause damage to my bacteria colonies...

:fish1:


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## mpodolan

Put it on the output side for sure. It may reduce flow, but shouldn't be too bad depending on your filter/size of the reactor/etc. I'd avise against putting any media (bioballs, pot scrubbers, etc.) inside the reactor. I stupidly did that with the first two I built. All it does is reduce flow further and clog up over time. The CO2 will dissolve fine without this stuff inside. Just my $0.02


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## coley24

Did you run your CO2 line into the bottom of the reactor since you have it on the output? I'm running a fluval 305 canister and the reactor i built is 12''. You've found the bio balls to be a waste? I have some being shipped to me as we speak so I guess that's a waste too...
:fish1:


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## mpodolan

coley24 said:


> Did you run your CO2 line into the bottom of the reactor since you have it on the output? I'm running a fluval 305 canister and the reactor i built is 12''. You've found the bio balls to be a waste? I have some being shipped to me as we speak so I guess that's a waste too...
> :fish1:


For the reactor, the idea is to run the output into the top of the reactor and have the CO2 enter near the top as well. This allows the CO2 to meet the incoming water. The CO2 will try to rise, as it is a gas, which allows it time to float around in the reactor and dissolve.

The bioballs aren't necessarily a waste, as they are decent bio media, but you'd be better off just putting them in the filter. Lots of people put them in the reactor, they just aren't necessary and could lead to problems (ie. clogging over time).


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## BiscuitSlayer

EdTheEdge said:


> Reactors are great. I know this even though I've never used one. The main drawback of this type of reactor is that you can not see what is happening inside.


Like Rex said, you can use clear PVC. I would disagree with it causing the reactor to cost 2 or 3 times as much. 1 foot of 2" clear PVC will cost on average about $6 plus the cost of shipping. I would like clear PVC just to see how nasty the inside of the reactor is getting.


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## coley24

mpodolan said:


> For the reactor, the idea is to run the output into the top of the reactor and have the CO2 enter near the top as well. This allows the CO2 to meet the incoming water


Sorry if this seems like a dumb question, but then the bottom of the reactor has the return line to the tank? Wouldn't this result in an extreme reduction in flow?

:fish1:


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## mpodolan

coley24 said:


> Sorry if this seems like a dumb question, but then the bottom of the reactor has the return line to the tank? Wouldn't this result in an extreme reduction in flow?
> 
> :fish1:


Yep, the bottom returns to the tank. I don't think this would necessarily make that much a difference. Actually, it seems to me that it would reduce flow further if the water was returned from the top, as the water would have to be forced upwards through the reactor (I'm really not sure, though. I'm sure someone more learned in the dynamics of water flow can help you out more)


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## CountViffer

I suspect that the flow will be slightly less when forced down through the canister, however I suggest this is more due to increased hydraulic resistance, brought about by having a longer outlet hose length(if necessary larger hoses would negate this).

However it stands to reason that the reactor MUST work this way around to obtain good dissolution of the CO2, as already stated the gas would just bubble straight up the water column otherwise.


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## FacePlanted

Footbeat: yes the mazzei works great, but there IS a very fine mist in practically all corners of the tank. It's invisible from a few feet away or further. You have to get pretty close to the glass to see the mist everywhere.


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## crazy loaches

I think one of the main ideas with the Mazzei is that it does create the micro bubbles. Many think that having some gaseous co2 in the tank in the form of micro bubbles helps plant growth above and beyond fully dissolved, but its often a trade off with tiny bubbles in your tank.


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## mrkookm

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## FacePlanted

Yes, the Mazzei has the capability to create bubbles that look like specs of dust particles. Extremely fine. Also if setup correctly, and so desired, it can even make the bubbles so fine that they completely dissolve before they enter the tank - practically no mist. Mine creates the "dust particle" size and some that are slightly larger - but still smaller than any glass diffuser I ever owned. I can't get them to completely dissolve even if I wanted them to - yet - but I'm wanting to get a stronger pump. Then maybe I'll be able to have that option if I want. But my whole point in getting the Mazze WAS the mist. I could never get mist in every corner of my tank with my glass diffuser - it just never produced enough mist. With the Mazz. I get 10X the mist that is 3X as small, without having to use more co2 to get it. My plant growth and pearling is explosive.


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## Rex Grigg

The reason you could not get the mist was because the CO2 was dissolving.


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## mrkookm

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## NyteBlade

I've actually been doing a bit of research about this myself. I've been using the Hagen ladder. The bubbles are still rather large at the top (at least compared to the pictures I've seen of the glass diffusers!) and usually a plant leaf got stuck in the thing, and that'd shut down the whole process.

I like the look of the glass diffusers and the CO2 mist, but besides aesthetics, I'm not too sure that serves any purpose. With the mixed reactions around here about the ceramic disks getting clogged, I'm rather nervous to spend $25 on something that may or may not work properly. Plus if you drop the thing or squeeze too hard, it's history. If you dropped one of the Rex Reactors, I'd be more concerned about the damage to the floor  

Sounds like the Rex Reactor will give you a 100% or near close efficiency. The only 'IF' (and it's a big 'IF') is whether I can assemble the thing and hook it up properly. I'll probably somehow manage to build up CO2 pressure until the regulator explodes and the entire tank goes flying through the wall or something :icon_roll


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## mrkookm

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## NyteBlade

mrkookm said:


> Yes it does get clogged but it works exceptionally well is properly maintained....at least IME. It not working is really dependent on you and how well you maintain it.
> 
> The Rex reactor is also another fine choice and prolly more 'you' if maintenance is an issue.
> 
> BTW i doubt you're gonna cause any sort of explosion :hihi:


What kind of regular maintenance do the ceramic disks require? Any particular brand that has a better track record than others, or are the Rhinox ones still the big sellers? :icon_wink


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## eds

Just I took a look at Rex's page. Have you seen the size of that thing? It's friggin huge. Scroll down and check out how it towers over his car. 

The one I made is slightly smaller...


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## mrkookm

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## mrkookm

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## Left C

NyteBlade said:


> What kind of regular maintenance do the ceramic disks require? ...


I clean mine when I do weekly water changes. I slide the diffuser up to near the top of the aquarium. I drain the water so that it is lower than the diffuser. When the water is below the diffuser; I pour hydrogen peroxide on the ceramic disc. I drain the rest of the water and I refill the aquarium. I slide the diffuser back down to it's normal place and start things back up. The little bit of hydrogen peroxide gets dissolved and it's no longer toxic. The ceramic disc stays pretty clean this way.


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## BiscuitSlayer

NyteBlade said:


> Sounds like the Rex Reactor will give you a 100% or near close efficiency. The only 'IF' (and it's a big 'IF') is whether I can assemble the thing and hook it up properly. I'll probably somehow manage to build up CO2 pressure until the regulator explodes and the entire tank goes flying through the wall or something :icon_roll


I built one and it works great. Simple to make if you have ever worked with PVC before. Simple to make if you haven't worked with PVC before. I was misting CO2 from a ceramic diffuser into the bottom of a powerhead and creating a micro bubble storm in my tank. I switched to the reactor only and I love it. I don't personally like the micro bubbles everywhere. My growth rate appears (to me) to be better than it was before.


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## 1shooter

BiscuitSlayer said:


> I built one and it works great. Simple to make if you have ever worked with PVC before. Simple to make if you haven't worked with PVC before. I was misting CO2 from a ceramic diffuser into the bottom of a powerhead and creating a micro bubble storm in my tank. I switched to the reactor only and I love it. I don't personally like the micro bubbles everywhere. My growth rate appears (to me) to be better than it was before.


Personally I think the inline reactor is the only way to go if you have a canister to hook it up with. Less clutter in your tank, low maintanance, and cheap.

If your unsure of building one Rex Grigg will sell you one for pretty cheap.


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## chatfouz

do any of yall have pics of full systems with the reactor? im a visual dude..


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## mrkookm

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## 1shooter

chatfouz said:


> do any of yall have pics of full systems with the reactor? im a visual dude..


Here's my setup. Keep in mind that I think you have some flexibility as far as how tall it is built to.


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## NyteBlade

Did anyone have any trouble finding the parts at their local Lowes or Home Depot for the Rex Reactor? I'm interested in building one, but hoping I don't have to go all over to find the correct parts...


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## 1shooter

NyteBlade said:


> Did anyone have any trouble finding the parts at their local Lowes or Home Depot for the Rex Reactor? I'm interested in building one, but hoping I don't have to go all over to find the correct parts...


Home Depot will have everything you need with the exception of the tubing for the co2.


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## gotcheaprice

Do they have hose barbs? That's the only thing I'm afraid they might not have. Also, what section would it be in?


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## crazy loaches

1shooter said:


> Home Depot will have everything you need with the exception of the tubing for the co2.



They have great tubbing for co2 (well at least Lowes does, not sure about HD), and its a heck of a lot cheaper than what rex and online shops sell. Polyethelyne. Like 9 cents a foot or less. Only downside is its really stiff and not available in colors. Lowes has all the hosebarbs I needed for various larger stuff (3/4", 1' vinyl tubbing, etc) but I didnt look for the small 1/4" stuff so not really sure on that.


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## Rex Grigg

If you need 5/8" barbs they can be hard to find.


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## Green Leaf Aquariums

You could try here maybe?http://www.plumbingsupply.com/barb.html


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## NyteBlade

Yeah, the house barbs are what I was worried about. I need the 1/2" kind for my Eheim 2213 I think. I'm sure Lowes/Home Depot would have just the regular hose barbs, but the 90 degree bend ones would be a lot nicer (and easier I think). Not too sure what the availability is on those...

I'll have to go out today and see what I can find.


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## mrkookm

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## NyteBlade

Then I guess once you get the entire thing built, you just drill a hole in the top, make sure the CO2 line fits in nicely, and stick that thing down about halfway through, hook it up to the outtake of the canister, and fire 'er away?

Hopefully it works and it won't cause too much wear and tear on the 'ol Eheim.


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## gotcheaprice

Thanks for the link! My rena xp3 uses 3/4 I think, so myabe my HD has them.


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## Rex Grigg

The Rena filters use 5/8". 

All the Lowe's and Home Depots out here quit carrying the 90° elbows.


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## gotcheaprice

arg, crap, I guess I'll have to order them online when I decide to make mine. You sell them don't you rex 
Could you throw in 2 into my order of the regulator? I'll pay for them (and if shipping is extra, tell me how much)
Also, how do you know what size barbs you're supposed to use. The tubing on the filstar says 3/4 in on the tubing, so I guess I must measure the inside of the lips?

I see your site says hose barbs for $0.50, but are those the same?


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## Rex Grigg

Those hose barbs are for CO2 tubing.

I have plenty of 5/8" elbows for reactors.

Unless Rena has changed the tubing they should use 5/8" as they are/used to be 16/22 mm tubing.


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## NyteBlade

I went to Home Depot yesterday and they only had brass of everything, and not even anything at 90°. Went to a specialty plumbing store, no dice there either.

Amazingly, Lowes had _almost_ everything I needed. I modified it a bit, but it's almost identical to Rex's. 

Basically, the Eheim 2213 hoses are about 1/2" according to the conversion chart. There weren't any 90° 3/4" to 1/2" hose barbs, but there were just plain 90° hose 1/2" hose barbs. Also, there weren't any 2" to 3/4" reducing T's.

What I did was bought just a standard 2" T, and put a reducer bushing in to make it smaller. In addition, I used 1/2" reducer bushings so I could just use the standard 1/2" 90° hose barbs.

Hopefully I didn't do something totally stupid and render the entire regulator useless. I'll have to take a picture later just to make sure I'm doing everything right.

By the way, for all those interested: Final bill was $11.15. I already had some 15" PVC pipe and pipe joint compound, but I imagine if you included those things, it'd be under $15. If it's as efficient as people say it is, having a solid, sturdy, long-lasting reactor that never (or rarely) needs to be cleaned that's not in the tank is pretty impressive.


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## gotcheaprice

Ah, yeah, it's 5/8.

The inner diameter is 16mm and the outer is 21mm. This is approximately 5/8" id by 3/4" od.


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## Algenco

NyteBlade said:


> I went to Home Depot yesterday and they only had brass of everything, and not even anything at 90°. Went to a specialty plumbing store, no dice there either.
> 
> Amazingly, Lowes had _almost_ everything I needed. I modified it a bit, but it's almost identical to Rex's.
> 
> Basically, the Eheim 2213 hoses are about 1/2" according to the conversion chart. There weren't any 90° 3/4" to 1/2" hose barbs, but there were just plain 90° hose 1/2" hose barbs. Also, there weren't any 2" to 3/4" reducing T's.
> 
> What I did was bought just a standard 2" T, and put a reducer bushing in to make it smaller. In addition, I used 1/2" reducer bushings so I could just use the standard 1/2" 90° hose barbs.
> 
> Hopefully I didn't do something totally stupid and render the entire regulator useless. I'll have to take a picture later just to make sure I'm doing everything right.
> 
> By the way, for all those interested: Final bill was $11.15. I already had some 15" PVC pipe and pipe joint compound, but I imagine if you included those things, it'd be under $15. If it's as efficient as people say it is, having a solid, sturdy, long-lasting reactor that never (or rarely) needs to be cleaned that's not in the tank is pretty impressive.


for the 2"to 3/4" reduction you need a bushing, Lowes has them


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## BiscuitSlayer

I found the 90 degree elbows at Ace Hardware. They had the 5/8" elbows which are still used on the Rena filters.


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## tama_drummer_73

*Question about reactor construction....*

Heya guys,

I am contemplating on building a reactor based on Rex's design somewhat. My biggest problem is vertical space. My question is do the reactors have to stand vertical or can they sit horizontal?


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## Green Leaf Aquariums

vertical..


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## NyteBlade

Hopefully it's okay to reply here with my final product. I just want to make sure my reactor was okay before I started gluing and assembling everything. It's almost exactly Rex specifications. I think the part I labeled is where the CO2 line goes  
Does the canister output go into side closer to the CO2, or the other side?


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## ValorG

The canister output goes into the side closer to the co2 line. This thing will be standing so you want the bubbles to come out closer to where the water will be coming into the reactor. Making the input face the same side as the output might be a bad idea but I dont know how your filter is set up. I have the input of my canister on one side of the tank and output on the other so I have my reactors barbs facing opposite directions (as in the top of my reactors elbow is facing left while yours in the picture is facing right.)


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## NyteBlade

So would the reactor look something like this when it's all done, or do I have it upside down?

The point you make about the hose barbs is a good one though. I'll have to see if I can figure out the best way to do it. :icon_surp


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## BiscuitSlayer

You got it Nyteblade. Your picture illustrates how it should be done. I believe that Rex drilled a hole with a smaller diameter than the tubing and just pulled it through. That might be a tad more difficult since you can't get inside the reactor now that it is built.

The other possiblity would be to use a pipe tap to cut threads into the pvc from a pre drilled hole and then use another small (1/8" hose barb with a threaded end?). That is going to lead to some PVC debris inside the reactor though.


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## NyteBlade

BiscuitSlayer said:


> You got it Nyteblade. Your picture illustrates how it should be done. I believe that Rex drilled a hole with a smaller diameter than the tubing and just pulled it through. That might be a tad more difficult since you can't get inside the reactor now that it is built.
> 
> The other possiblity would be to use a pipe tap to cut threads into the pvc from a pre drilled hole and then use another small (1/8" hose barb with a threaded end?). That is going to lead to some PVC debris inside the reactor though.


Thankfully I erred on the paranoid side. I just pieced the PVC together loosely. Nothing is glued together yet. It's a good thing you mentioned that though. I would've probably assembled it without thinking about the CO2 line.

I assume the best way is probably to just do the Rex method of pulling the CO2 line about halfway through? The only issue I can think of is reusablility, but CO2 line isn't prohibitively expensive, and I'm sure there's some way to connect 2 pieces of CO2 line together :icon_wink

Although you do have quite a nice design there too, BiscuitSlayer with the T and the CO2 hose barb.


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## BiscuitSlayer

NyteBlade said:


> Thankfully I erred on the paranoid side. I just pieced the PVC together loosely. Nothing is glued together yet. It's a good thing you mentioned that though. I would've probably assembled it without thinking about the CO2 line.
> 
> I assume the best way is probably to just do the Rex method of pulling the CO2 line about halfway through? The only issue I can think of is reusablility, but CO2 line isn't prohibitively expensive, and I'm sure there's some way to connect 2 pieces of CO2 line together :icon_wink
> 
> Although you do have quite a nice design there too, BiscuitSlayer with the T and the CO2 hose barb.


Ah.... You are all set then! I thought you had used the cement already.

As far as connecting the two pieces of tubing goes you might want to go ahead and do that with a check valve :icon_wink .

Thanks for the design compliment. The only two things that I don't like about mine are that the CO2 hosebarb I used is brass and I didn't get to implement my design exactly as I had hoped. The brass hosebarb is actually much more complicated than it looks. It is connected to a brass coupler where I used a pipe tap to thread the opposite side to connect another brass hose barb. My intention was to connect another hose to the other side connected to a limewood airstone or a small ceramic diffuser. I scraped the idea though because I couldn't fit the limewood airator through the 1/2" hole.


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## Kayakbabe

If you read the literature on your cannister, you'll see you should not plump inline on the intake. For the eheim filters it is becuase it will put a lot of stress on the impeller motor. Plumb on the outflow instead. 
Yes, it is true that plumping things inline reduces the flow. Anytime you add more surface area, or anything not in a straight line... as in longer tubing, more bends, elbows, etc. you increase friction and that reduces flow rates. Bends and elbows create slower flows becuase they cause turbulence in the stream of flow. Turbulence slows things down too.
It's simple hydrodynamics at work.


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## Bowles42

I was curious is anyone had experience with a Rex Reactor on an Fx5. How big of a reactor would I need? Rex expressed to me that it could possibly screw with the computerization of the Fx5, so if someone had actually done this first, I wouldn't have to experiment.


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## NyteBlade

Kayakbabe said:


> If you read the literature on your cannister, you'll see you should not plump inline on the intake. For the eheim filters it is becuase it will put a lot of stress on the impeller motor. Plumb on the outflow instead.
> Yes, it is true that plumping things inline reduces the flow. Anytime you add more surface area, or anything not in a straight line... as in longer tubing, more bends, elbows, etc. you increase friction and that reduces flow rates. Bends and elbows create slower flows becuase they cause turbulence in the stream of flow. Turbulence slows things down too.
> It's simple hydrodynamics at work.


Does putting a reactor on the outtake create any stress on the motor? I'm a bit worried about blowing up my Eheim. I guess if it's a choice between putting undue stress on my Eheim or messing with those finnicky ceramic disc things, I'd probably take the Eheim option.


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## pvtschultz

You can't put "stress" on a centrifugal pump since it'll keep spinning anyways and there is a lot of clearance inside on them around the impeller. All things should be plumbed to the outlet of any pump since an increase in suction head can be detrimental to a pump and cause erratic operation. Also, a pump has more "power" on the pressure side and very little on the suction side.

I just built a 2" x 24" reactor for my 90 but I am still working with it. When I get it tuned in, I'll post pics since it is a step away from Rex's design.


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## NyteBlade

pvtschultz said:


> You can't put "stress" on a centrifugal pump since it'll keep spinning anyways and there is a lot of clearance inside on them around the impeller. All things should be plumbed to the outlet of any pump since an increase in suction head can be detrimental to a pump and cause erratic operation. Also, a pump has more "power" on the pressure side and very little on the suction side.
> 
> I just built a 2" x 24" reactor for my 90 but I am still working with it. When I get it tuned in, I'll post pics since it is a step away from Rex's design.


So I guess I'm not causing any additional wear and tear on the Eheim if the reactors on the outlet? :thumbsup:
Outside of a reduction in flow, there's no downside?


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## pvtschultz

Nope, you just added head so that reduces flow. That's just the nature of pumps.


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## killudead

ok, so what does the size of the pvc pipe matter, what effect does it have it you use a 1" pipe instead of a 2" pipe?


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## brohawk

Big pipe = small bubbles. Small pipe = bigger bubbles, since the flow in the reactor is stronger, and can push them sooner through the reactor, before they dissolve completely.


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## killudead

ok, that makes sense, So would a bigger pipe slow down your water flow even more. At which would you add koralia's?
or could you add another inline pump?


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## grumbolar

Sorry to steal into the thread, but I have the fluval 305, and the hoses are the plastic "ribbed" kind, and obviously won't seal with a regular hose barb like a rubber hose will. Anybody have a solution to plumbing the reactor into fluval hoses? I can follow directions fine but I'm not much of a plumber so I know I'd end up with wet floors if I try to experiment.


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## Jeff5614

I have a reactor inline with a 404. You can use fluval tubing as long as the rubber connectors are still attached. If not then just get some clear 5/8 inch ID tubing from Home Depot, Lowes, etc. It works fine. I use clear vinyl from the canister to the reactor and fluval tubing from the reactor to the tank. If you need more help I'll see if I can come up with a pic or two since it might be better than my explanation.


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## emmanueln

In my thinking if the water flow is high in th reactor more co2 will get dissolved
well the thread was quite informative for me.I have ahiem 2213 with max mix ista external in line reactor for my 25gal tank, i find it reduces the flow at about 25% the impeller of the reactor move quite slowly so can it mix the gas well ?


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