View Full Version : c02 vs oxygen

10-21-2010, 12:41 PM
Hey guys, when I'm running co2 on my tank during the day I can easily maintain the recommended 30ppm- when the co2 and lights turn off for the night, it appears that my co2 levels barely even drop over the night. I'm glad my c02 levels are constant- but I'd like to see a decrease so I know there's plenty of oxygen for my fish.

I'm thinking about running an airstone at night which will most likely make my co2 levels drop more drastically.

Basically, should I aim to keep the co2 levels constant 24 hrs a day? Or is it ok to get a drop at night?

10-21-2010, 12:53 PM
O2 and CO2 levels are independent of each other unless the levels get to saturation which is not going to happen, soda is not even at 100% CO2 saturation.

As long as the CO2 stays below 50ppm you should not have any troubles. If you had plenty of O2 before you added CO2 you still do.

High CO2 levels can be and are dangerous but not because they reduce O2 levels they are dangerous because the fish becomes unable to remove CO2 from its blood stream and exchange it for O2 which is what cause the poor fish to suffer and then die.

10-21-2010, 01:38 PM
I see- but if I ad an airstone won't that disturb the surface which will in turn allow more co2 to escape? Basically I'm just wondering (now that I know my fish have enough oxygen) if its harmful to have a co2 level that fluctuates at night or if its better to just keep it as stable as possible. Sorry if I sound redundant :p

10-21-2010, 01:54 PM
I turn my CO2 off at night just a waste of gas. I turn it on an hour before lights on. As long as the levels are stable when the lights are on you will be fine.