What is the purpose at all of leaving on CO2 24/7?

[jblasto]

I have the capability to trigger my CO2 on about an hour prior to lights and turn off with the lights. Currently I'm running it through the night (unlighted) which is 16 hours. Seems like a waste of CO2 to be using my tank 16 hours a day if the plants can't use it. What is the purpose at all of leaving on CO2 24/7? Besides the slight shift in PH when it's lights out? I guess what I'm trying to get at is if you have a ph controlled system (like I do) and a solenoid which can be hooked up to a timer (like I do) then would I be CRAZY not to just run the CO2 lets say 10 hours a day and the lights 8 rather than throwing away half my tank in to the dark?

I'm assuming people that are pumping it in 24/7 don't have the capability to put it on a timer or am I missing something here? This is my first CO2 planted tank.

[Fuzz]

if you run your CO2 24/7, you are definitely wasting your CO2...plants will absorb OXYGEN at night time and release CO2. Also, if you are running your CO2 all day and night, you will most likely kill your fish because they won't be able to breathe.

I didn't run a ph controller, but I had mine on a timer. I had to keep an eye on it for a few days to make sure that I didn't push too much. A few times I had my fish gasping at the surface and had to either close the needle valve a bit more or make the timer shut the CO2 down at that time of the day to compensate.

people that run their CO2 all day have no idea what they're doing and definitely didn't do any research.

[emc7]

I think people who run it 24/7 don't have the capacity to put in on a timer and don't want to do it manually or invest in more equipment; CO2 is cheap compared to a broken valve or dead fish from spilling your DIY bottle. If your cO2 is so high you'd kill fish at night, turn it down. You don't want dead fish if your light dies.

[grogan]

No no no! Only run your CO2 while your lights are on. Get a timer and set it accordingly. Have it turn on one hour before the lights turn so the system is fully saturated by the time they do come on. Then have them turn off one hour before the lights shut off so the CO2 is consumed by the plants before lights out. Leaving it on all day will over saturate the system, killing fish and causing algae blooms. I also have a air stone pump oxygen to aerate the aquarium and allow the excess CO2 to escape AT LIGHTS OUT. The best way to do this have another timer hooked up to the air pump and set for the times that CO2 is not being added.

[BV77]

Grogan said it all.