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CO2 Injection In Sump Options

jagillham

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6 May 2015
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343
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Kent (UK)
Hi all,

I’ve a 5ft tank (~450l), soon to be heavily planted with 90l sump. I know an in-line reactor would be the best option for CO2, but due to my set up will be a bit of hassle to get the pipe work sorted for that, plus the expense of buying or DIY’ing the reactor.

A cheaper and more convenient option for me would be placing an atomiser in front of the return pump. Has anybody had any success with this before, and also how does the bubbles in the tank compare to an in-line, and also just an atomiser in the main tank itself?

Thanks
 

foxfish

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11 Oct 2009
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There are lots of post about doing just that, there are a few variations to the theme... needle wheel pump being the most dedicated but an inline atomiser or a fine air stone will work as a compromise ...
FABA8C97-D560-4AB6-A6DF-8F7F86546A2B.jpeg
 

jagillham

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6 May 2015
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Kent (UK)
Tried to have a search for this, but no avail...

Is it possible to inject the CO2 into the down pipe coming into the sump? My logic here is that it would work very similar to a reactor in that the bubbles can only exit down once they are dissolved. There would be no issue with gas accumulating at the top of the reactor, as any excess would simply exit back into the weir.

The CO2 filled water then has to pass through the sump, before through the return pump and into the tank, which should greatly assist with any remaining micro bubbles.

Any downsides to this method?
 

foxfish

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Surly there are many soft drink bottles that will do the job ... the selection is vast!

C02 is the fizz in a fizzy drink so if you shake the bottle and open the lid, there will be a large release of C02 into the air.
That is what will happen if you pour it down a drain so i doubt if placing a diffuser in the overflow would work very well as the gas will just rise the the surface and disperse into the air, what does get into the sump will then rise to the surface and disperse ..

However, I have no idea how your system works, what your overflow looks like of if your sump is covered, so there might be a slim possibility it would work?

I have used the plastic bottle taped with stretchy electricians tape method many times, it works very well, it is a very direct and simple method but will still show micro bubbles in the main tank.

You can even just stick the C02 air line straight into the pump inlet without any form of diffuser or drill a hole in the top of the inlet and feed the gas directly but you will get larger bubbles in the tank.

A hight pressure atomised inside a plastic bottle neck will work equally as well as an in-line atomiser or slightly better in fact but, they all produce a mist ......
 
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jagillham

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@foxfish - I probably didn’t explain myself very well.

I did try the atomiser in a bottle option, but unless the atomiser was directly infront of the return pump the bubbles were not getting pulled into the pump at all (Eheim compact 3000). They just sat at the top of the bottle before finding their way out in a big bubble back out the wrong way. I therefore did away with the bottle and just attached the atomiser to the return pump inlet.

What I was trying to suggest was not injecting the CO2 in the overflow, but near the base of the pipe that takes the water from the overflow to the sump (at below the water level of the sump). This would mean the bubbles have to either float up against the flow for over 1 meter of head height to end up in the overflow box. Or, go down, through all the sump, then the return pump, to end up in the tank.

The idea is to remove the micro bubbles if possible.
 

foxfish

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Ah ok... well unfortunately I don’t understand that at all :) but, as I said I don’t know how your sump is set up?

Are you suggesting that the pipe that runs verticals down from the overflow box is completely full of water?
I have never used an overflow that works like that!
Are you saying the C02 won’t rise up to the surface of the sump compartments when your pump would not pull it a cm inside a bottle?

The bottle neck you pictured is simply to big diameter and allowing the gas to rise up rather than be pulled in, a smaller diameter bottle will work.
However that is a little pointless as the method will always produce some mist unless the return pipe is very long!

Perhaps consider a reactor, they are not so simple to use or make but you won’t get any mist.
 

Wolf6

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My plan is to go for bottle/atomizer as well, with most of the sump covered with an acrylic lid. If the bubbles arent sucked into your return, perhaps try a bottle with smaller diameter so the flow is stronger? If my primary plan doesnt work, I intend to use 2 CO2 sets, one near the inflow (like your idea) and one at the return, still using the bottle. But thats only if the bottle/return solution proves insufficient to achieve my desired 20/25 mg CO2.

You could also have a small separate pump going from your sumps' out-chamber back to your in-chamber and attaching an inline diffusor to this tube, someone suggested that in another thread about this subject. That is my other backup plan :)
 

Easternlethal

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15 Mar 2016
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I also run a sump and also spend a lot of time wondering how I can increase co2.

The main problem is that co2 always tries to find an equilibrium with how much there is in the air, which is why it escapes so easily and sometimes doesn't even dissolve.

Scientists measure the rate at which gasses stay in the water according to various factors. One of the most important is actually pressure, which is why sodastreams are so efficient at carbonising water.

If you want to improve co2 intake the best way is to find out where pressure is greatest in your system and inject co2 into that. For a sump that's usually the outflow because it has to push so much water out. You can increase efficiency even more by using a tiny nozzle. In some cases that's even better than a reactor because pressure always beats surface exchange everytime (which is what you get with poorly designed reactors that don't create sufficient pressure).



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