DIY Co2 Question/?////?//

[ghengis]

some do the airline tubing into the intake of their HOB but i see that as a waste since it just escapes the filter by the impeller and you get minimal diffusion.
What you can do in your case is get a limewood airstone (wooden one, not those blue/black ones) and add it at the lowest point in your tank, right below the filters over flow. The airstone will create micro bubbles which once they rise will be pushed back down into the tank by the overflow of the filter.

The upside down cup/bell is pointless since water movement and size of the gas bubbles is what will give you maximum diffusion.

Isn't there an issue with the surface agitation of the HOB causing the CO2 to gas off before it can be effectively distributed? Also, in my experience with HOBs, there is a fair amount of oxygen introduced as the water falls back into the tank, which would also serve to nulify the CO2... Just a thought. I guess a way around this would be to keep the water level such that water doesn't so much fall from the filter as run out into the tank...if you know what I mean...

 

[jmhart]

Isn't there an issue with the surface agitation of the HOB causing the CO2 to gas off before it can be effectively distributed? Also, in my experience with HOBs, there is a fair amount of oxygen introduced as the water falls back into the tank, which would also serve to nulify the CO2... Just a thought. I guess a way around this would be to keep the water level such that water doesn't so much fall from the filter as run out into the tank...if you know what I mean...

Yes, that is the issue with the HOB. If you only have an HOB, you can still maintain decent levels of CO2 by diffusing the co2 through an airstone as far away from the HOB as possible. And, as you suggested, keeping the tank as full as possible is best.

 

[gmh]

I have a piece of driftwood with a hollow area underneath. I wonder if the CO2 would diffuse better if the airstone were in the cave and the bubbles had to migrate out? (Sorry if I am highjacking the thread).

 

[DAVIDFBT]

It will all be pointless since you run a sponge filter, and I assume you have it hooked up to an airstone/air pump. This will take out the CO2 that has been dissolving in your tank.