How to balance off O2 vs CO2?

[nickmcmechan]

Hi,

I have a 180l SA setup which I've ordered a pressurised CO2 kit for.

I run the tank at 32 degress C, which of course lowers dissolved O2, therefore I run air into the tank via the outlet of the powerhead. This causes a lot of surface agitation.

I experimented with turning of the air pump yesyerday and woke this morning to find all the fish hanging at the surface. Immediately I put the air pump back on and the difference was instant.

So, how do I run an air pump into the tank as well as CO2 injection without gassing off too much of my CO2?

 

[PeterGwee]

Make sure you have enough surface movement will prevent fish issues with low O2. Yes, it will drive off a bit of CO2 but you can always add a tad more to make up for the small amount loss.

Regards,
Peter Gwee

 

[nickmcmechan]

thanks peter

i was thinking about getting something to redirect the pump output downwards so some of the o2 will dissolve before rising and making agitation

guess i should have the co2 output at the opposite end?

 

[VaughnH]

O2 isn't very soluble in water, about 1% of the solubility of CO2. So, adding air bubbles to a tank doesn't add much O2 by dissolving it from the bubbles. But, the air bubbles do create lots of water surface movement, and that is what increases the amount of O2 dissolving into the water. But, since CO2 goes into solution in water so easily, it also comes out of solution equally easily, so the air bubbles can remove CO2 too. Therefore, it is better to just ripple the water surface a bit with the water flow from the filter or a powerhead to get more O2 into the water. Air bubbles are for non-CO2 or non-planted tanks.