Is it safe to leave CO2 on 24 hours?

[murphys33]

Hi all,
Have been puzzled with a question adn hope some experts here canshed some light - you see, one controls PH via CO2 injection in a planted setup right? IF CO2 is only injected during lights on period, would that not mean that when lights and CO2 are off, the PH may potentially swing? Alsoof CO2 is left on 24 hours so as to control PH swings, would the fishes in the tank not run out of Oxygen? the CO2 injection may displace some of the O2 in the water... Pls enlight. thanks

[tawauboy]

when lights and co2 are off, the ph will swing. but will not affect the fsh too much. the only way to minimise or eliminate ph swing is to use a ph controller. an expensive solution.

if co2 is left on 24 hours, then you will have to adjust it such that the co2 concentration just before lights are switched on does not exceed toxic levels. the level should be > 30ppm.

co2 does not displace o2. they are independent of each other.

[geoffrey]

Swing can be minimise by using buffers such as baking soda, coral etc.

[hmph]

try pumping air thru an airstone in the night......should be good enuff

[hwchoy]

don't inject CO2 when lights are off, use a solenoid under timer control.

[vinz]

Yes, pH will rise once the CO2 injection is stopped, but it should be quite slow. As long as you have a KH of at least 1, the pH will not change enough to harm the fishes. Without the KH, the pH will swing much more, possibly to the detriment of the fishes.

CO2 will not displace the O2 in the water. However, if you leave the CO2 on 24hrs, there is a chance that the CO2 levels may get so high that the fishes suffer CO2 poisoning.