TPIRman

Hi all,

A couple days ago I set up a DIY inline CO2 reactor for my 30G using Ghazanfar Ghori's plans -- basically a 10"-long, 2"-diameter PVC pipe filled with bio-balls and sporting a hose connector on each end. Your run-of-the-mill DIY reactor. My only variation from Ghori's plan was that instead of gluing the airline connector directly into the pipe, I just drilled a small hole and pulled some airline tubing through. (It still forms an air-tight, gas-tight seal.) Otherwise I followed the prototype in the link exactly.

After testing for leaks, I put the reactor on the intake line of my Eheim 2213.

The CO2 is being produced by a DIY setup (2 x 2-liter soda bottles) and generates about 1.5 bubbles per second.

I was surprised to find that over about a day of operation, the noise from the reactor went from silence to a slight trickling noise, to something approaching a waterfall. Finally I turned off the Eheim to let the trapped gas escape -- causing a _lot_ of large bubbles to shoot out the intake hose!

After getting all the gas out of the reactor and the intake line, I started things up again. And once again, the trickle noise is slowwwwly getting louder.

Since Ghori states in his plans that he has one of these reactors hooked up to the intake of an Eheim 2213, I didn't think flow rate would be a problem. Nor did I expect that 1.5 bps would be excessive CO2 input.

I don't have anything between the intake and the reactor -- in fact, there's no other non-standard equipment anywhere on the filter line. So what am I doing wrong?

Thanks in advance for any suggestions!

niko

TPIRman,

I had to deal with a similar problem using a commercial inline "Turbo-Jet Reactor". That reactor is supposedly better than the reactor that you have made. The difference is in the way the water flow passes through the reactors. The "Turbo-Jet" has the water flow injected from the side AND close to the wall of the reactor. That creates a circular water motion as opposed to a straight flow out of the DIY model. So the CO2 bubbles should disolve better. Also in the "Turbo-Jet" reactor the CO2 is being injected using a very fine ceramic air stone.

Any of the above features didn't make the "Turbo-Jet" a perfect reactor. Reducing the gas flow or decreasing the pump rate didn't resolve the problem either. One can speculate that the gasses that accumulate are not CO2 but some rather inert gasses, but that is just a speculation and it really doesn't matter - the problem is there and as to be fixed.

I resolved the issue by connecting the solenoid of the CO2 regulator to a timer that shuts the CO2 for 15 min. every hour. The pump is always running so the gasses that accumulate in the reactor are being dissolved or pushed out.

One last comment - here in the US some of the parts that are suitable for making a DIY CO2 reactor are made of copper. It is not a good idea to use them since invertebrates are sensitive to copper.

--Nikolay

pineapple

I always find it difficult to understand the logic of putting an inline reactor on the INPUT side. I should do some more research on this issue before committing to 'paper'. But it occurs to me that the following all apply. Correct me if I am wrong:

- bacteria in a filter need oxygen - not CO2. Adding CO2 to the input is, therefore, not helpful to the biological filter. Is there even a Ph issue to consider as well?

- although water entering a filter should be pretty clean and free of debris, it is not entirely free of gunk. Rather than have an inline reactor on the input side acting as a prefilter, which needs cleaning more regularly, why not have it on the output side which, in theory, delivers cleaner water?

- The 'pull' of a filter pump on the input side is?? surely about the same as the 'push' on the output side in terms of power.

- the risk of having a filter fill up with gas bubbles is far greater when the reactor is on the input side. Risking have disruption in the flow-through does not seem worth it to me.

What am I missing? There must be some absolutely critical reason that so many people prefer to use the input side rather than the output side for inline reactors.

Andrew Cribb

TPIRman

The assumption here is that CO2 displaces/reduces the concentration of O2 -- this is not the case. The pH swing that results from CO2 injection does not have an adverse effect, either. If your CO2 levels were too high, your fish would suffer before your bio-filter.

Yup -- this is a concern that Ghori and others have acknowledged. In Ghori's case, he said that it did not clog after months of use with just the Eheim strainer on the intake hose (probably because bio-balls make a terrible mechanical filter). If it ever did get gunked up, I would just remove it and run some water through at high pressure. Others who are more cautious put a sponge prefilter on the intake.

A properly-built reactor will have dissolved all or most of the gas before it reaches the filter. Even though in my case some of the gas is apparently _not_ being dissolved, it is still remaining in the reactor. With Eheims specifically, the risk of locking up is very low anyway because Eheims are engineered to prevent airlock. Prior to installing this reactor, I had the CO2 going directly into the filter, with no problems aside from the occasional "burp" (which unfortunately meant wasted CO2).

My reasoning, and I think the general reasoning as well, is that CO2 goes up, whereas water on the intake side goes down. So putting the reactor on the intake provides an easy way to create more turbulence for the CO2 bubbles. Of course, you can have the water flow down the reactor on the output side as well, but it is more of a hassle.

So that's the rationale. But all of this is not to say that your idea of placing the reactor on the output side is necessarily a bad one -- I'm considering that as a solution to this problem. But before I get into the PITA process of removing the reactor and putting on the output side (and jury-rigging a downward water flow, I'd have to convince myself that it would make a difference.

Niko -- thanks for your note. Glad to hear someone else has had a similar experience. Unfortunately, since my CO2 is produced by yeast generators, the solenoid solution isn't available to me. Also, rest assured there's no copper to be found in my generator -- plastics from top to bottom!

Ghazanfar Ghori

The trickle noise will occur when there is a gas build up in the reactor.
There's been some discussion about the possibility of it actually
being O2 outgassing from oxygen staturated water.
Although I havent got conclusive proof, a few observations seem
to favor that theory.

My CO2 is on 24/7 on the 2213 - yet I only get the trickle noise
late in the evening - by morning the reactor is silent again.

Soon after 50% water changes, I get trickling noises in the
reactor. Tap water is under pressure and contains a lot of dissolved gasses. When exposed to regular atmospheric pressure, the
gasses come out of dissolution. You can see that - plants pearl
like crazy after a water change - water is saturated with O2
and cannot dissolve the O2 produced by plants - causing the pearling.

Seems that it is quite likely that the reactor, besides dissolving gasses,
also takes gasses out of solution and collects them - causing the
trickle noise. When saturation levels drop, the gasses dissolve
back into the water and the trickle noise stops.

All this is a theory...don't know exactly what's happening in there.

Corigan

I run my DIY Reactor on the output of the eheim. I notice bubbles getting blown from the spray bars from time to time. Putting it on the output lets it outgas by itself gradually over time. Atleast this is what I have seen in my experience. I would try putting it on the output of the 2213, then you don't have to worry about all that gas being sucked into your eheim.

Matt

Ghazanfar Ghori

When I first designed the reactor, it was to be on the outflow side
of my Eheim. The design was slighty different - since I had to route
the outflow back to the top of the reactor.

Two issues I've noted when putting the reactor on the outake side...

1) Decrease in outflow. This was probably caused by the increase
in head. Let me explain that a bit...
Let's say the reactor is 12" long. When placing it on the outflow,
mounting the reactor vertically, the Ehiem has to pump the water
up to the top of the reactor, then it flows back down 12" and then
pumped back up the extra 12" - increasing the head by a foot. That
siginificantly reduces the amount of water the pump is able to move.

However, you may be able to counter this by elevating the filter
by the same height as the reactor - if you've got the space
under the cabinet for that.

2) Not as simple a design as when placing it on the intake. I'd rather
keep it really simple - less chance for making mistakes that can
cause leaks.

In the end - do what works for you. People have tried both designs
and both seem to work well.

pineapple

TPIRman,

Thanks for the responses to my points above.

I did not realize it was possible to run CO2 into an inline reactor from a DIY yeast CO2 set up. You have more nerve than me. Using DIY CO2 can be a bit up and down in terms of bubble supply depending on the mixture, the age thereof, and the temperature prevailing. I assumed (obviously wrongly) that a slightly higher consistent pressure of CO2 than available via DIY means was necessary to inject into a reactor. One lives and learns...

Andrew Cribb

gpodio

Removing some or all of the bioballs will work too, this will allow the smaller bubbles to get sucked into the canister and eventually back out to the tank avoiding accumulation of gasses in the reactor. This was the same problem I had with my powered reactor. You really have to take your pump into consideration when placing bioballs in the reactor, you don't want to stop all bubbles from escaping the chamber, just the larger ones. Too many bioballs for your flow rate will allow gasses to accumulate.

Hope that helps
Giancarlo Podio

TPIRman

Hi all -- this is a while after the fact, but I wanted to thank everyone for their responses in this thread. It seems from my further experience with the noise that Ghazanfar's theories as to the source of the trickling is right on. It seemed suspicious that there would be excess CO2 gas anyway, since CO2 is absorbed so easily into water. The trickling noise does indeed become more pronounced shortly after a large water change, and is more prominent during the day.

Giancarlo, your suggestion seems reasonable, but unfortunately the reactor is now sealed up, so I'd have to build another one if I were to connect my mistake. I had never figured that the bioballs would cause the water to de-gas. How many bioballs would be appropriate for an Eheim 2213, I wonder?

I think I might try elevating the Eheim somehow in order to place the reactor on the output side of the filter. Though I'm still not entirely convinced that this will eliminate the problem, it seems like a reasonable thing to try. If that doesn't work, I think I will just use a limewood airstone below the filter intake (hopefully this will minimize "burps" while still providing a high level of absorption). My goal with the inline reactor was to get equipment out of the tank, since space is at a premium in a 30G, so I don't want to bother with one of those ugly powerhead/gravel-vac tube contraptions.

Thanks again.

-John