How Does an External CO2 Reactor Work? (e.g., Dupla, AquaMedic)

[DTs]

I have the large external Dupla CO2 reactor with the bioballs in it and was wondering how it works.

The instructions don't say much other than it should be completely filled with water when working correctly.

My guess is that as CO2 bubbles are injected from the top of the unit, the water flowing down the unit keeps it suspended and it bumps into all the bioballs, helping it to dissolve better in the water.

Is this correct?

One thing I haven't figured out yet is if I flood the entire chamber with CO2, forcing the water to exit the unit, and then turn the CO2 off, and subsquently increase the water flow to the reactor chamber, it fills up again with water within seconds, but where does the CO2 go? It certainly is not going back out to the tank, or I would see bubbles coming out. It's almost as if there's a venting valve somewhere letting it escape.

 

[bobalston]

In the situation you mention, it would seem that the co2 is getting disolved. There ain't no other place for it to go.

Bob

 

[DTs]

My thoughts exactly, but believe me, it's not dissolving that fast! The entire chamber of CO2 evacuates in about 10 seconds.

The CO2 has to be venting somewhere. When I get home from work, maybe I'll stick the whole chamber in a bucket of water and repeat the CO2 filling/evacuation process, and see if venting occurs.

 

[plantbrain]

CO2 dissolves very fast, especially if the water doesn't have much in it.

Example: you can watch a CO2 bubble(1/16" dia) disappear as it floats up say 20" depth. That takes a few seconds.

Regards,
Tom Barr

 

[DTs]

Could about 1,000 bubbles be absorbed into the water from a reaction chamber, say in 10 seconds?

FWIW, my dKH is 4 (Salifert test kit), temperature is 78, and pH 7.1.-7.2

 

[carpguy]

You're filling the entire chamber with gas and forcing all the water out? That's definitely not how they work…

You can then fill the chamber with water in ten seconds without having the gas forced into the outlet? Even if you had a significant leak a lot of the gas should be bubbling out the return…

A thousand bubbles all at once aren't going to even think about fully dissolving in ten seconds. Most of us are bubbling 1 or 2 times per second. Maybe 3. Not a hundred.

The water bucket is a good way to check for leaks, but I still feel like I'm missing something…

 

[DTs]

Just filling the chamber with gas as an experiment. I run it normally with the chamber full of water.

Gas bubbles should be forced out into the tank when I fill it with water, however none are coming out. This must mean there's a gas leak/venting going on somewhere. Need to figure out where though.

 

[plantbrain]

Well try it and see, I have used reactors and often they fill in the evening, then the Reactors are shut off at night and then they dissolve away rapidly within a few minutes/seconds when they are turned on in the morning.
Your water is seriously low in CO2 also.

So yes..........I am right or you have a leak.

To rule out a leak:
If you have a leak, there's sure to be some water on the floor when they are full is this not true? Since water fills it and where water can go, so can gas.

Especially if the reactor releases all that gas in 10 seconds.

To check further for a leak, use some soapy water, and dribble some over any region you believe is leaking.
If it's leaking, you'll see bubbles.
And then perhaps we will see if I was right or not.

Regards,
Tom Barr

 

[DTs]

Plantbrain - I totally agree with your comments!

Something has got to be wrong with my reactor, or either I'm doing something very wrong. If I turn the CO2 off most of the day, my CO2 is 7.2. If I turn it on at 4 bubbles a second for a newly planted 90g tank (e.g., no major growth going on yet), my pH is 7.2. This tells me that CO2 is not dissolving in the water to any great degree.

The reactor instructions mention that if there is any air in the chamber when starting it up, to invert it, and the air will discharge. I thought perhaps I'm running the reactor upside down, but according to the illustrations, I'm doing it correctly.

I still need to put the reactor in a bucket of water and see where the gas is venting. Didn't have time last night. I'll give it a shot tonight.

 

[plantbrain]

No bucket needed, just put some soapy water on it now and see.

That will tell you if you hasve a leak somewhere, simply wipe off later.

Should only take 5 minutes tops.

Regards,
Tom Barr