Co2 And 02

[tom_os]

surely if you are adding carbon dioxide to a tank to help plants, then you are loosing oxygen needed for the fish?

is this right?

 

[Truck]

surely if you are adding carbon dioxide to a tank to help plants, then you are loosing oxygen needed for the fish?

is this right?

nope you can have high levels of cO2 and O2.

 

[tom_os]

oh ok

 

[Bignose]

Physically, with the amounts and purities available to home fishkeepers, the adsorption of one has a negligible amount on the adsorption of the other. When you start approaching full adsorption (like if you used a lab-grade cylinder of pure CO2 or O2 and a very high injection rate), then there will be some limiting effects, but for home fishkeeping purposes, the adsorption of one is negligible to the other.

Now, what I suspect you were thinking about, however, is the fact that in general when you inject CO2, you attempt to minimze surface disturbances so that you give your water the greatest chance to adsorb the CO2. And yes, that minimized surface does reduce the amount of O2 that will be adsorbed into the water. Or, vice versa, if you have a lot of surface agitation, you get good oxygen transfer into the water, but less CO2 adsorption because the CO2 bubbles escape faster. That does happen, and so with the typical setups -- injecting CO2 and letting that ambient air provide the CO2 -- it is very difficult to keep both the CO2 and O2 adsorption levels high. But, there is nothing physically limiting preventing both levels from being high -- just the setups of most people tilt the balance toward one or the other.

 

[aaronnorth]

Plants produce oxygen as a by-product of photosynthesis, so this will help to keep the O2 levels raised, even if you do have minimal surface agitation because of CO2 injection