"Nikki Casali" wrote in message
...



BIG SNIP


What were these CO2 levels? I'm wondering the safest, highest level of
CO2 I can have in my tank, taking into account inaccuracies of pH
measurements, before it poses a danger to the fish.



As I understand it, CO2 doesn't push out O2. The level of O2 is determined
by the gas exchange at the surface with the additional O2 from the plants.
The amount of CO2 is independent of O2, I thought. At night, O2 is taken up
by the plants, so I think most people turn off the CO2 injection at night,
since it isn't being used by the plants, anyway.

Here's a good link:
http://faq.thekrib.com/plant-co2.html
Down near the bottom

Regards,
Susan