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Venturi Line on a Rex Style Reactor

757 Views 6 Replies 6 Participants Last post by  Wasserpest
I am going to build an external reactor to plumb in-line with my Fluval and am trying to decide on the design. I imagine in general it will be based on a rex style reactor. I have read a number of posts on Tom Barr's reactors that include a venturi line to outlet collected gases. However, these were internal reactors. Has anyone included a venturi line on an external reactor? Is it necessary with a rex style reactor?

On a separate note, it seems that some people at bioballs to help diffusion. For those that don't, are you getting adequate dissolution?
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Collected gases are not normally a problem with my design. In fact if you do have collected gases in an external reactor IMHO you either have a poor design or did something wrong.

And I've built around 30 reactors. Only put bio-balls in the first. And the CO2 dissolves just fine. A basic understanding of physics will tell you why the bio-balls are not needed.

The water flow is from top to bottom. The CO2 injection point is midway down the water column. The CO2 tries to rise. The water flow just keeps rolling the bubbles around as they dissolve.
Has anyone included a venturi line on an external reactor?
I have a Venturi line going into my external reactor.

It works with the design of my reactor.

Never having used an external reactor as you describe, I can't speak of Venturi efficiency on one of those.


Do you mind describing the design of your external reactor? I'm interested to see how others are including a venturi on the external reactor.
On the Barr internal venturi reactor the venturi line tends to generate only CO2 mist, and that is easily carried out into the tank. If that is your desire, then I don't see a good reason why it couldn't be made to work, but I doubt it improving the already very high efficiency of the Rex style reactors.
I'd recomend against any media in an external reactor. I find that even though it's on the filter outlet it seems to collect debris. Its then released any time the reactor is disturbed. Pretty messy. My first reactors were made of 4" PVC. I've now reduced them in size so they are just large enough for the heater that fits into a compresion fitting in the top. Like Rex I have to agree they work perfectly. The only time mine collect extra gas is when I knock the needle valve messing around with the plumbing.

I believe the venturi on Toms reactors is way the CO2 is injected.
There is a long discussion about adding a venturi loop to an external reactor. Not because it is necessary, but to create fine bubbles. I don't see much reason for it, but if you are interested read through the discussion there.

Adding anything into the external reactor to improve dissolution isn't necessary if the flow rate and pipe diameter are right. Bioballs and such effectively reduce the diameter of the reactor, which speeds up the flow, plus it adds some restriction to the filter outlet, increasing the backpressure to the filter.

For internal reactors with an open bottom, you can add a venturi loop to reduce gases (O2, mainly) collecting on the top, which might increase CO2 dissolution. As for the usefulness of little bubbles, decide for yourself.
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