Aquarium time lapse - The effects of water circulation and surface agitation on CO2 level.

Aquarium time lapse - The effects of water circulation and surface agitation on CO2 level.
The green square in the middle is a reference color showing a high level of CO2.
The video begins with the circulation pump turned off. There is CO2 injection, so the CO2 level is high and goes up through the day as CO2 is added. At night, the CO2 injection is turned off.
When the circulation pump is turned on at the end of day 1 in the video, the CO2 level drops to almost zero during the night, and at day it starts at almost zero, then slowly rises, but not to the same level as without the pump running. Compare with the green reference square to see the difference.
When the circulation pump is turned off again, the CO2 level rises to the desired level again, and is not lost during the night.
At night, there is no CO2 injection (it is turned off), but the plants produce CO2 rather than consuming it. During night, when the pump is running, the CO2 is completely removed from the water, so when the next day starts, the CO2 levels starts at zero. When the pump is not running, the CO2 is not lost during the night, and the day starts with a decent CO2 level.
Conclusion: If you add CO2, then have very little surface agitation, otherwise the CO2 will be almost completely lost through the water surface to the air, and the aquarium plants won't benefit from that.

[@songikiu]

Could you please make a test with a fan only. I'm using fan for cooling without pump, just curious how it's effect co2 level.

[@pablo1gr1]

where did you get that co2 meter?

[@chn65]

+Pablo Gomez It came with the CO2 set (JBL proflora)

[@ssss-df5qz]

I'm having problems with maintaining a decent co2 level during the day because of my sump. Since it's open to the air and the water falls over the baffles (and also the upper overflow) it seems to completely counteract the co2, even at 4bps my drop checker stays a turquoise color.
I've adjusted the outlet of the pump so it doesn't agitate the surface in the top tank and that seems to have helped a bit. I think next I will fit my in line co2 diffuser in the hope that the water oxygenated by the sump is infused with co2 before it gets back into the tank... or maybe make the sump air tight to an extent?
Either way I know I can't afford to run 4bps+ :/

[@chn65]

+ss ss It's important to use the right CO2 diffuser / reactor. I use the Aqua Medic Co2 reactor 1000, and it gives good results. I can use only half the dose now.