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Discussion Starter · #1 ·
I have been bubbling CO2 into my tank for a while now with one of those glass diffusors. I got tired of burning through tanks so quickly and decided to try building an inline reactor based on Rex Grigg's design.

It doesn't seem to be working as well as my diffusor, I'm trying to drop the pH down by about 1.5 points. Any suggestions on tuning it? I've adjusted the flow through it so that CO2 bubbles are just barely not being forced through the outlet. The bubbles per second is rather high, can't really count it.

Details:
90 gallon tank
Danner model 7 pump

CO2 reactor:
Made out of 1.5" diameter PVC, about 2.5 ft tall.
3/4" inlet, 1/2" outlet
Water flows from the top to the bottom, CO2 enters from the side of the pipe about 3 inches above the outlet.
CO2 regulator is on a timer, about 12 hours a day.

Thanks!
 

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CO2 enters at wrong spot or possible too high flow would be my two guesses at the problem. Theory is that the CO2 enters and tries to float upward while meeting the downflow of water. As long as the bubbles are large they stay in the pipe But when they enter at the bottom, they get pushed down and out. Also many people make a modification that is thought to be better and use a fitting for the CO2 tubing. This fitting often lets the gas enter along the side of the PVC where the water is less likely to catch the bubbles.
For a solution, I would suggest cutting the PVC near the top, leaving enough space to put it back together with a coupling. Then drill a hole smaller than the CO2 tubing. Cut the tube at a sharp angle so that you can fit the tip through the undersized hole and grab it with long nose pliers to pull it on inside enough to reach the center of the PVC. It should be somewhat difficult to pull in. This makes a watertight seal. Once the tubing is installed repair the PVC with a coupling. Fill or seal the bottom hole. When choosing where to drill, don't forget to figure in the space for the repair coupling?

Looks like this maybe?
 

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I believe PlantedRich is referring to the side inlet on the RGR below. I have yet to actually test it out yet so I have not idea how it performs. It will be going on my planted grow out tank that is not yet operational. I also have several cerges reactor that also are not in action. I wanted to compare the two since they are the two most commonly used in the hobby.
 

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Discussion Starter · #4 ·
Ah, I do have a fitting instead of just sticking it in the pipe. I was planning on putting a little bit of tube on the other side of the fitting, but forgot to do that before gluing it all together. Before I dismantle the whole thing to fix that, I'm going to try tilting it a little so the bubbles come off the wall and up the water column instead.

The other thing I'm trying to avoid is having a CO2 pool at the top because that would make noise with the water entering. That was my reasoning to have the CO2 inlet near the bottom... the bubbles float upwards as the water moves downward (ideally keeping them stationary) and they dissolve before they reach the top. I guess the idea with having the CO2 enter from the top is that as the bubbles are forced down by the down flowing water it dissolves before it reaches the bottom?
 

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I agree mostly with Rich. I think you need to stick the tube straight in so that the air enters in the center of the tube. If it does not then it can easily 'sneak' up the side and pool at the top of your reactor.

I also agree with Rich's design in the fact that there should NEVER be an elbow at the top of your reactor. It should be a straight connection so that it is impossible for bubbles to pool there and create an air pocket.

However, I do think it is better to put the CO2 line as low as you can afford to put it to maximize contact time in the reactor. Too low and some bubbles will sneak out. Too high and you minimize contact time and your reactor is less effective.
 

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Klibs--- Can we think over the part about the contact time being low when the CO2 enters too high?
I think that it will work out that increases rather than decreases the contact time. If the CO2 enters low, it can be blown out and go to the tank. But if it enters high and then tries to float up, it meets the water coming down and has to stay until the bubbles get small enough to not have the buoyancy to float up and are small enough to go down.
I see it as a fight between two forces. Water entering wants to carry the bubbles down. They want to float up but as they adsorbed, they loose the ability to float and lose the battle to the water flow?

But then I should say that it is not my design. Rex did the design.
 

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I did a bit of "paint" to show what I think happens on reactors. Bear with the drawings , please. Not pretending to show all, just the basics of the idea. Also, this is really not my plan as Rex Griggs did work out most of the plan and I have only made a small change which I admit decreases the water flow somewhat.



In my opinion?
On the left is a reactor using a fitting for the CO2 and placing it near the bottom. The fitting lets the gas enter and begin the trip near the wall. This is an area where water flow tends to be slower and with less turbulence. I feel this is what causes some of the complaints about noisy reactors as the gas can go to the top and form a bubble where incoming water splashes. When the gas enters near the bottom it is more likely to be drawn out the outlet where it shows as bubbles in the tank. It tries to go up but it isn't very far to go down and out? Like getting caught in a Tokyo train at rush hour! You don't always go where you planned.

Center is the design I like better. The design at left has an elbow at the top which causes loss of flow. I use a straight fitting and form the tubing in a large curve which slows flow less. I want as much flow through as practical. I use the original Grigg's design for putting the tubing in trough an undersized hole and drawing it to the center of the water flow. Many feel this may leak but it is a proven design that DOES NOT leak. The water flows faster at the center and the gas entering higher makes it harder for it to go down and out. The hope is that flow and bubble size will force the gas to stay in the chamber until it is no buoyant enough due to decreasing bubble size and then passes through in bubbles too small to see in the tank.
On the right, the design will give better flow but I like to be able to set the reactor on the floor rather than strap it up to use a straight fitting. A cap was the first thought but those are often curved. To get a flat surface, I went with the plug.
 

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If you are trying to lower the PH by means of co2,it's not going to happen.
I tried that same thing several years back,all it did was waste co2.
The high PH problem is most likely the substrate.
 

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Critique this one rich???

This could be dangerous territory. Some could be asking for an honest opinion which I might offer but then there are also those who might want me to be drawn into saying it might not work , only to tell me it does fine!

On basic ideas, I might see several of the things I mention that I might have been done different. The sharp elbows, short length, slope and fitting might make me think it would have problems. But the big thing about all this is that each reactor has to work with what we each have. More or less flow from differing filters, how much room is available and lots of little things can factor into how well it works.

If interested in do-overs, I would look at longer length in most cases as I find no problem with CO2 in contact with the water longer. Longer exposure just makes it diffuse better. Straight in using big gradual loops in the tubing might get better flow and the true vertical makes the CO2 stay better and fight harder to go up than the slope might.
But if it works, there is no reason not to love it!!


On the question of changing PH, I would disagree. I find CO2 does make a change in the PH. The drop checker works on this idea. It changes colors when the PH has dropped one full point. That is thought to be about 30PPM in our tanks. PH controllers like the Milwaukee sense the PH to turn CO2 solenoids on/off.
 

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This could be dangerous territory. Some could be asking for an honest opinion which I might offer but then there are also those who might want me to be drawn into saying it might not work , only to tell me it does fine!

On basic ideas, I might see several of the things I mention that I might have been done different. The sharp elbows, short length, slope and fitting might make me think it would have problems. But the big thing about all this is that each reactor has to work with what we each have. More or less flow from differing filters, how much room is available and lots of little things can factor into how well it works.

If interested in do-overs, I would look at longer length in most cases as I find no problem with CO2 in contact with the water longer. Longer exposure just makes it diffuse better. Straight in using big gradual loops in the tubing might get better flow and the true vertical makes the CO2 stay better and fight harder to go up than the slope might.
But if it works, there is no reason not to love it!!


On the question of changing PH, I would disagree. I find CO2 does make a change in the PH. The drop checker works on this idea. It changes colors when the PH has dropped one full point. That is thought to be about 30PPM in our tanks. PH controllers like the Milwaukee sense the PH to turn CO2 solenoids on/off.
That's what I wanted to hear, truth is good. I will flip it vertical, it's been working pretty darn good so I'll probably leave it in place after the adjustment, I'll get antsy and most likely replace it soon enough anyways. Thanks. It has bioballs in there to battle the co2 bubbles too.
 

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You sound like a guy that is going to do good with DIY stuff. Lots of this stuff is a design and sometimes it is just right. But if not, I always figure I'm going to be doing something that may change it anyway!
Tipping the reactor vertical may help if you are getting bubbles out into the tank but it is not a real big, big, thing. Just a bit easier to push down and out to the left than if it had to push them straight down and out.
Is that a Sun or Aquatop filter peeking out? I've not used a reactor on them but since they sometimes give a bit more flow than The Eheim 2217's that I've done, I could see they might have enough flow to pass some bubbles. It really is a thing that has lots of little things that make it work or not.
Part of the flow problem is just due to the way fittings are made. If we take a 5/8 tube and stick it on a 5/8 fitting, it would sound like there is no loss. But the truth is obvious when you pick up a fitting and try to look through. A 5/8 fitting IS 5/8 but only on the outside. The inside gets lots smaller. Too bad there isn't a practical way to put a coupling over the outside of tubing to connect them without reducing the interior size.
 

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You sound like a guy that is going to do good with DIY stuff. Lots of this stuff is a design and sometimes it is just right. But if not, I always figure I'm going to be doing something that may change it anyway!
Tipping the reactor vertical may help if you are getting bubbles out into the tank but it is not a real big, big, thing. Just a bit easier to push down and out to the left than if it had to push them straight down and out.
Is that a Sun or Aquatop filter peeking out? I've not used a reactor on them but since they sometimes give a bit more flow than The Eheim 2217's that I've done, I could see they might have enough flow to pass some bubbles. It really is a thing that has lots of little things that make it work or not.
Part of the flow problem is just due to the way fittings are made. If we take a 5/8 tube and stick it on a 5/8 fitting, it would sound like there is no loss. But the truth is obvious when you pick up a fitting and try to look through. A 5/8 fitting IS 5/8 but only on the outside. The inside gets lots smaller. Too bad there isn't a practical way to put a coupling over the outside of tubing to connect them without reducing the interior size.
I'm a contractor by day so I'm no stranger to building haha.. i made a different type for my smaller 20t. This tank in question is a 30l. I have an ac70 running with a hydor koralia 240, the can is a sunsun304b.. i got the can solely to load with purigen and bio media.. and of course fuel a diffuser. The flow was insane at first, I over drilled the spray bar and now it's ever so subtle.. the plants gently sway and the DC is lime green, plants pearl.. i feel it will be even better once vertically orient the diffuser. I will be mounting it's little brother next to it. Same deal.. for bio media, purigen and a reactor, slowed flow is actually a plus in this case!
 

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Good deal. You've pointed right straight at why advise and designs have to be fit to each situation. For me reduced flow is bad while it is good for you in your situation.

Now if I could find that magical fitting that goes on the outside of flexible tubing without restricting the inside. On 1/4" it would be a compression with some type of sleeve inside but then I don't find them in 5/8".
That's why we call contractors when we want build the "dream home"! :help:
 

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Good deal. You've pointed right straight at why advise and designs have to be fit to each situation. For me reduced flow is bad while it is good for you in your situation.

Now if I could find that magical fitting that goes on the outside of flexible tubing without restricting the inside. On 1/4" it would be a compression with some type of sleeve inside but then I don't find them in 5/8".
That's why we call contractors when we want build the "dream home"! :help:
You need the fittings that come on canister filters huh? I'll start digging! or a large style compression fitting...
 

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Not really needing any fittings right now. It's just one of those nagging things I wish for when I try to put two tubes together without losing any flow. I assume about half the flow loss at the 90 elbows is from reducing the inside opening as much or more than the turn.
 
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