Negative Pressure Diffuser for Yeast CO2 - The Planted Tank Forum
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post #1 of 2 (permalink) Old 02-05-2011, 10:05 PM Thread Starter
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Negative Pressure Diffuser for Yeast CO2

After much tinkering I finally found a co2 diffusing method for yeast set ups that's far more efficient than anything short of a reactor. Although what it doesn't diffuse it makes up by creating a negative pressure environment. Meaning that your bpm is going to be upped. The yeast containers don't have to build up pressure to overcome water pressure anymore.

A word of warning: You need sturdy yeast containers to do this otherwise you're going to end up with crushed containers and a flooded tank of yeast juice.

The materials are:

1.) A strong power head. This one is ~120gph.
2.) Pantyhose
3.) Tubing to fit onto your ph's intake

The principle is based on a venturi. water flowing past a smaller opening will create a vacuum.


1.) cut an appropriate length of tubing. The shorter the better. The deeper the co2 tubing has to go into the water, the great pressure it must overcome. This is an important concept. It will partially allow you to control the amount of gas that will be vacuumed out of your tubing. Tinker around with lengths.
2.) cut an x or t shape into the side of the tubing so you can jam your air hose in with relative tightness.
3.) rubber band a bit of pantyhose around the intake end of the tubing. The panty hose serves as an anti shrimp chum maker and to raise the vacuum power.
4.) attach the apparatus to your ph and you're ready to go.

I can't guarantee this to work on all set ups but it has for me, very well.

Here is a video of it working. Sorry about the Darth Vader breath. I have a cold.

The tank is only 3 weeks old so there's still dead leaves on the hair grass from going emersed to immersed so please excuse that.
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post #2 of 2 (permalink) Old 02-05-2011, 10:48 PM
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i use a very similar setup on my 50g corner tank the outlet of my diy Co2 is plumbed into the venturi port on my internal filter it works great especially if you aim the flow into the path of a spray bar that sprays downwards to push the bubles down into the water column giving them a greater chance of dissolving.

at one stage i used a gravel vacuum approx 50mm diameter with a short piece of clear tube attached to the outlet of the filter... with the vacuum pointed down towards the gravel it meant that the Co2 was trapped in the 50mm diameter tube with water constantly flowing through. It was an incredibly effective reactor but very ugly so it is gone now.

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