# Inline CO2 problem with XP3



## helgymatt (Sep 12, 2007)

I have a DIY inline CO2 reactor like the ones described in some of these forums. The reactor is 10" long 2" pvc filled with 11 large bioballs. I am putting about 2 bps into the reactor to keep the co2 levels at about 30 in my 55 gallon. It is on the intake of my Rena xp3 with the flow going down and the co2 going into the reactor from the top....just as everyone recommends. My *Problem *is that I still have huge amounts of CO2 bubbles coming out of my output very frequently in the later half of the day. I am confused as to why this only happens later in the day, but I suspect it is when enough CO2 builds up in the top of the xp3.

I am trying to figure out what I can do to solve this problem. It is obvious that the co2 is not getting dissolved in the reactor, but I don't understand why because many other people using the same reactor and similar flow filters have 100% dissolution of CO2. What are others experience with this? Have you had to decrease the flow of the filter or modify the reactor somehow (would be hard to do now)? 
Matt


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## hoppycalif (Apr 7, 2005)

This type of reactor works best on the outlet of the canister filter, and the water should go from top to bottom, with the CO2 bubbles entering near the bottom and floating up against the water flow. With a Filstar XP3 you need a bleed valve at the top and it needs to be open when you prime the filter. Otherwise it won't prime. It took me over an hour and many futile attempts before I learned this.


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## helgymatt (Sep 12, 2007)

To do what you recommend...can I just flip the reactor upside down (so the co2 input is at the bottom) and change it to the output. I have also read people squealing about a loss in flow when the reactors are on the output. Is this true or not? Oh and what can I use for a bleed valve and how would I attach it (keeping in mind that I don't want to have to build a new reactor)? Would it be something that I would drill into and use a tap bit or something I could put inline with the hose? A picture would probably be worth a thousand words. 
Thanks for you help.


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## hoppycalif (Apr 7, 2005)

Without seeing a photo of your reactor it is hard to know how best to make it work better. But, you will probably want to visit a hardware store and see what tiny little valves they have, then get one that looks promising as a bleed valve and from that, figure out what fittings, drilling, tapping, etc. are needed to install it. You can always add a tee fitting to the top of the reactor and use one leg of the tee for the bleed valve. Look through this thread and you will find my photos of how I added the bleed valve: http://www.aquaticplantcentral.com/...rojects/2958-diy-inline-reactor-plans-12.html


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## JohnInFlorida (May 12, 2007)

Mine is also on the output of the XP3 ... and I had the same problem that hoppy is describing and my solution was also a bleed valve. You can see it in this picture sticking out of the left side of the reactor almost at the top. In my case, I drilled a 1/4" hole for the bleed valve, installed it with a little pvc cement and now if the pump won't prime I just hold a towel up to the valve, open it till I get water instead of air/co2, close the valve and it's done.










Anyway, I am able to get adequate levels of co2 in both my 55 and my 180 using reactors plumbed like the one in the pic without any bubbles making it to the spray bar.

Keep Smilin'
John


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## mikenas102 (Feb 8, 2006)

John, that's a nice, clean plumb job you did there. I wish I had the room under my stand to do the same. I have a Turbo Twist UV on the output of my xp3. I don't have a bleed valve setup though. The UV does make it difficult at times to prime the filter but it's not impossible.


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## hoppycalif (Apr 7, 2005)

When you have been injecting CO2 into the reactor and have a bubble at the top, that seems to air lock the system, so there isn't enough head pressure to prime the filter. Priming is just the head of water from the water inlet in the tank down to the filter driving water thru the filter, and almost filling the return hose too. If there is no gas bubble in the reactor I think it would prime without the bleed valve, but the bleed valve is the only way to get rid of any gas bubble. At least it is the only way that doesn't result in a big mess of spraying water.


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## ponyrandy (Jan 13, 2007)

My thoughts are that the reactor's length may be too short for the amount of flow that the xp3 puts out. Even so, like hoppy said, move it to the output. Leave it as it is with the output from the filter going in at the top and also the co2 going in at the top. Remove the bioballs to keep from restricting the flow, the co2 bubbles should stay suspended in the reactor until they are dissolved. I used a fitting with a 1/2" fpt connection built into it and just used a tee for the co2 input on one side and the bleed valve on the other like this: http://www.aquaticplantcentral.com/forumapc/attachment.php?attachmentid=5148&d=1186635916. I think your initial assumption is right though, the gas is building up in the filter and by relocating it to the output should solve the problem.
Brian


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## hoppycalif (Apr 7, 2005)

The benefit of having the CO2 enter near the bottom is that, with a transparent center tube, you can see the bubbles and have a visible indication of how much CO2 you are adding without using a bubble counter. The bubbles don't get swept out the bottom in any case if the center tube is a 2" tube.


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## helgymatt (Sep 12, 2007)

Thanks for all the suggestions and the pictures are worth a thousand words. Some very nice set-up/plumbing many of you have. 
I set the reactor at a slight angle last night and I'll see tonight how the co2 is disolving before I go to all the work installing it on the output and using a bleed valve. Currently I don't have to have a bleed valve because the reactor is on the input. I think I may be making a trip to lowes to find some more plumbing supplies, however. I'll be sure to reply how it all works out. 
P.S. What is an easy way to upload pictures on here. I tried yesterday and my file had to be like 100kb. With that size I could barely see the picture! There must be a differant way?
Matt


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## Left C (Jun 14, 2005)

Wouldn't using an Eheim Installation Kit #2 help, as with mikenas102's priming problem by having an inline UV installed? The kit has a removable cap to burp the system. Would it help with someone that has a CO2 reactor installed inline on the output too or as well?










They're on sale at the Drs. The 16/22 mm kits for $16.79 fit the xP's. http://www.drsfostersmith.com/Produ...ll&Ntx=mode+matchallpartial&Np=1&N=2004&Nty=1


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## helgymatt (Sep 12, 2007)

Here is my CO2 reactor modiefied with a bleed valve and switch to the output. I have to wait till morning to see how well the CO2 is disolving. 
http://www.aquaticplantcentral.com/forumapc/aquarium-pictures/displayimage.php?imageid=4812


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## helgymatt (Sep 12, 2007)

I am still not getting 100% of the CO2 dissolved. I am really confused now. Bubbles are coming out of my spray bar...only when the CO2 is on. I tried with the co2 coming in at both the top and the bottom of the reactor, which there was no difference. You can see my reactor in the picture I posted earlier. Correct me if I’m wrong, but this looks exactly like all the other ones I’ve seen. At this point I am just going to deal with the bubbles and forget about getting 100% dissolution. The only last thing I can think of is removing the bioballs. This would require building a new reactor and I really question if that that will improve anything. I would think that the bioballs slow the flow even more and enhance dissolution. It seems like I just did a lot of work for not much improvement. 
Matt


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## vicpinto (Mar 27, 2007)

Matt,

The spray bar has a flow adjustment valve. Is it open all the way? If not can you give me a rough indication of how open it is?

The XP3 is a powerfull pump. With my XP3 I have noticed that if this valve is closed beyond a certain the the flow becomes too restrictive. At this point the pump impeller cavitates the water. What you may be seeing is air bubbles and not CO2. Try turning off the CO2 for a day while maintaning the flow adjustment knob at it's current position and see if you still have bubbles.

Victor


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## hoppycalif (Apr 7, 2005)

Rex Grigg is very insistent that bioballs or other stuff inside the reactor is of no benefit. It just reduces the water flow rate that gets to the tank from the filter. The slowing down of the flow in the reactor is a result of the large diameter of the reactor tube. If it is 2" in diameter, and the filter hose is 1/2" in diameter, the flow velocity in the tube is about 1/16 of what it is in the filter hose. That is adequate to allow plenty of CO2 to dissolve into the water. I don't know if that is the problem you have or not. Mine has nothing in the tube and it works fine.

Perhaps you should just ignore the bubbles. The goal isn't to achieve 100% dissolution of the CO2, but to reach the ppm of CO2 in the tank water that you want, in a reasonable time. CO2 is cheap, so wasting some isn't a problem. Why not concentrate on hitting the amount of dissolved CO2 you want, as measured with a drop checker, and forget the bubbles?


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## vicpinto (Mar 27, 2007)

JohnInFlorida said:


> Mine is also on the output of the XP3 ... and I had the same problem that hoppy is describing and my solution was also a bleed valve. You can see it in this picture sticking out of the left side of the reactor almost at the top.
> John


John,

Interestingly on my XP3 the intake is the left nozzle.


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## helgymatt (Sep 12, 2007)

I don't really want to mess with my reactor anymore or drag on about this any longer so I'm just going to go with what Hoppy said and just "deal with it". It isn't really a problem, I am getting plenty of CO2, but I was only wondering "why" this is happening. 

Victor, my valve is wide open (actually I removed the valve because it is pointless to have in the tank if I don't use it). I'm fairly certain it isn't oxygen bubbles, because it goes away shortly after I turn off the CO2

I'm also wondering why there is such a big issue using bioballs or not(I guess I'm still dragging). If I have bioballs inside the reactor, which supposedly slows the flow, what would be my benefit of removing them? Isn't a slower flow going to dissolve more CO2 than a faster flow? Note: I'm not trying to say it wouldn't work perfectly without them. 
Cheers everyone for your comments


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## ponyrandy (Jan 13, 2007)

The principle behind the reactor is for the bubbles to hang in the water flow. That is the reason the intake is at the top. With the water flow going down, the bubbles try to rise and they dissolve as they hang in the flow. I believe in Rex's advice that anything in the reactor just slows flow down. Having said that, if the reactor is too short or the filter is too strong, slowing down the flow might not be a bad thing. Someone posted a thread the other day for some reactors that I believe were on a European website. One of them had a bypass line with a valve to adjust how much flow goes through the reactor and how much gets bypassed. I thought this was an interesting idea, as I had never seen this before. Anyway if you should decide to build a new reactor in the future you might consider a few things. First is to invest in the clear PVC. It really comes in handy for times like this. I just take a flashlight and back light the tube and I can see exactly whats happening in the reactor. Second is to use a 2" T on the bottom and install a cleanout plug. This does 2 things, it allows you to add or remove bioballs and also gives you a way to clean the inside of the reactor. The third thing is to make the reactor a little longer. I don't know of any disadvantage to doing this but the advantage is the co2 has to hang in the flow longer until you get the dissolution that you are looking for. Hope this helps.
Brian


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## ponyrandy (Jan 13, 2007)

Just another thought. What if you were to restrict the line between the filter and the reactor by squeezing it slightly with something like a pair of needle nose vice grips. If this solves the problem it definitely would be a too much flow problem. 
Brian


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## ponyrandy (Jan 13, 2007)

I found the thread with the reactors that have the bypass line: http://www.aquaticplantcentral.com/...zing/44328-aquamas-external-co2-reactors.html
Brian


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## FacePlanted (Aug 13, 2007)

could it be that in the morning, the reactor is running at 100% efficiency and dissolving all of the co2 because the co2 concentration is low in the morning. Then later on in the day, the co2 levels have risen and it becomes harder to dissolve the same amount of co2 into the water and so the reactor is running at like 90% efficiency. So since the co2 doesnt dissolve as easily b/c of the increased concentration, the bubbles aren't dissolving as fast inside of the reactor and are eventually just being blown out of the spraybar? I am using a glass diffuser and would love to have co2 bubbles blowing all over my tank. I think the plants would love it...bathing in co2 bubbles.

I dunno. I'm not really a co2 scientist, so this is just how I would understand why this condition is occuring in your tank....I don't know for certain. ???

:-k :noidea:

I do think a bleed valve is necessary for excess gas build-up, and for priming the filter.
Check this out--this reactor has some mods that it says helps with co2 dissolution, decreases backpressure, and less gas lock.
http://www.barrreport.com/articles/3444-dual-venturi-diy-external-co2-reactor.html
Definately worth a look at the pictures.

Good luck!

-Mike B-


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## JohnInFlorida (May 12, 2007)

vicpinto: as you said, interesting, but I'll bet it just that one of us was standing on his head when we looked ... 

just kidding ...

I'm looking at mine like pic 1, perhaps you're looking at yours like pic 2?

pic1









pic2









I wouldn't expect that they make them both ways.

Keep Smilin'
John


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## vicpinto (Mar 27, 2007)

Oops! I messed up. I have my reactor positioned to the right on the XP2 as in pic1 so assumed the right nozzle was the outflow. As it is the outflow is the left nozzle and cuts across the unit to the reactor.

My bad.


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